To just not really have my kids ‘ under control ‘ a lot of the time.. 3 and 5 years old

Eek. OP came here being vulnerable and asking for advice. You've given her advice from a very particular school of parenting - which people here may or may not agree with - but fair enough, she specifically asked for advice and you gave it.

However, the tone in which you've dispensed your wisdom has been incredibly belittling. And in several of your responses, you've implied (on the basis of precious little) that parents have monumentally failed their children by not being strict enough by age 3, and will be lucky to claw it back now.

There is a certain "brand" of midwife who treats their vulnerable patients just like that - making them feel like they've failed as a mother even before they've started. Perhaps you're kind and supportive at work. But it's ever so tempting to join the dots here...

Of course children can be very spiteful. You’ve never seen a young child poke or push a pet or sibling? They have very little empathy, big frustrations and a need to test boundaries. Of course they can be deliberately peevish. There are generations of children’s literature that characatures it!

Yes, @MyOliveHelper is just enjoying being dramatic (and not very nice).

Wow you sound full of hate. Unruly I would give you, but spiteful? Where has OP or anyone given information that could lead you to call such young children spiteful?

"tonight my 5 year old said I’m ’hurting Her feelings’ because I shouted."

Oh that's a shame - you hurt my feelings when you were rolling about on the grass and not listening.

I’m not surprised they’re on the wild side. They’re 3 and 5 and no doubt razzing each other up all the time! The 5 year old is probably acting sillier because he has a younger sibling too.
Anyway all you can do is be really firm
about your expectations and start punishing them for pissing around. The penny will drop but you have to be really consistent and really quite strict to get them to learn and comply

A lot of this is true. You had said you apologised when you shouted? Yes later on I would explain why I shouted but you need to feel in charge here. You don't have to be their friend all the time, not at this age. Sometimes you just lay down the law and that's it. Whatever you say is what everyone does..if not have some consequences... go home/no icecream/no tablet or tv. Whatever it takes.

If you can take one kid out at a time and just practice the basics. So go to yhe shop and they either have to hold your hand, hold the trolley or stay close. Don't actually go for a real purpose, go as a training exercise. Then eventually do it with both kids when they both understand the expectations.
Before getting out of the car I ask my two the question, 'what do we need to do to be successful?' Taken time to get them to give me the answers but repetition works.
If either of my two don't listen, then they have to hold my hand, no option, no conversation, taken straight back to the car/house on the school run.
While walking out of school I have points they can run to safely, they birst out of school with so much energy! So our school has two gates, they have to stop at the first gate and wait for me to catch up, then second gate, then tree. Cross the road and then to each tree down the road type of thing. Sometimes they need guidance like be a dinosaur, who can be the fastest, walk backwards (slows them down), crab walking. Eldest is 6 with adhd, so I need to focus his energy or it is mayhem!
I still have so many doubts and I swear my kids seem 'more' than any of the others. But I now remind myself that these rebellious, energetic balls of crazy will work to their benefit in the real world... I'll suffer a bit longer and try not to knock it out of them haha!

My 3 year old likes to run off a lot, it used to be terrible but I'm just super strict now. If I say she has to walk next to me, but she runs off - she has to hold my hand. If she won't hold my hand then we go straight back to the car immediately or go home. If it's somewhere I can't go home from (like the school run) then I tell her she won't get any chocolate / TV / whatever her favourite thing is that day, and I mean it.
Unfortunately it does mean being quite brutal and following through consistently, but now they are much better as they know what will happen if they don't behave.
Of course, she's 3 so still needs reminding regularly not to run too far ahead, so it's about being realistic too. I used to use the buggy often purely for crowd control when she was smaller because I could strap her in for times when I needed the safety net. You could take a buggy and tell them if they don't stay with you, they'll get strapped in the buggy!
Just start being consistent and follow through with consequences.

Sorry haven't read all the replies so probably repeating others but yes mine were like this despite me being quite a quiet reserved person. They're generally much better now, especially separately, but can still be a handful together, they just get very very silly with each other. My older one is like a Duracell bunny, just never seems to get tired.

I don't have all the answers but my suggestions:

Accept that children are different and you don't have quiet calm children. As someone else said some little kids will just sit and colour and some won't. So be realistic and avoid situations where they are expected to sit down and be quiet. I never took them out to eat except to McDonald's when they were that age, especially both together.

Pick your battles: rolling around and bouncing in an area with plenty of space - fine (even if it's embarrassing to you, believe me I've been there...). Rolling around and bouncing by a road/in the path of an unsteady elderly person= not fine.

Safety first: backpack reins for 3 year old and strict staying nearby rule for 5 year old when near roads/crossing roads.

Spend many many hours in play parks/soft play/swimming/whatever else burns off energy safely. Outdoors in all weathers. We still don't do 'quiet days at home' like some families seem to manage and my older one is 11...!

Choose what you most want to work on first and come up with a strategy for that, don't try to 'fix' everything at once.

(Sorry if I missed this somewhere but are they both boys by any chance...?)

Oh, this takes me back! Mine were like this, two boys, same age gap. They didn’t run off exactly, just played together and ran around me all the time instead of doing anything practical / helpful. I had to get stricter the following year when I had a third and needed tighter control of them plus a pram!

You’d have to try telling them clearly what you expect of them later at pick up, set boundaries and stick to them, praise good behaviour etc. Or, let them play as long as they’re not in danger. Mind are 12 and 10 now, good friends most of the time, and save their wrestling and playing for the weekends. It’s a phase.

And no to whoever said that, I'm a midwife who is regularly trying to stop "spirited" older children hurting their heavily pregnant mothers or newborn siblings.

I said that when people say "a bit of spirit", as the poster who I quoted did, other people woukd use the terms I used to describe them. That was a general comment about people who use comments like that, or "boys will be boys", or "she knows what she likes" etc.

But none of what @jomek described is remotely "spiteful"?!

Rolling on grass? Running around for Ten Minutes before bedtime? Call the police 🙄

Op I think they're probably high energy, impulsive little kids and likely egging eachother on.

It's actually kind of great the 5 year old is able to be honest and try to articulate what goes on in their head. It's probably true! She probably knows in quiet, in between moments or if asked, how to behave, she maybe even realises after the event, but in THAT moment, running around after her sibling or rolling on the grass after being in school just seems so darn tempting!

How are they in school/nursery? Are they easier one to one?

What are the consequences of running off currently ?

Clear expectations
Praise/reward the behaviour you want
Firm and immediate consequences and you must follow through every time

That sort of thing does happen with DS @Thatsalineallright ; he will get an idea into his head and it can be difficult to reason him out of it. His dad is the same <sigh>

I think most kids are like this, my eldest was and now he’s grown into a normal teenage boy. It’s just a phase.

Fair enough. Maybe pick up the cheapest bottle you can find and let him use that for indoors? But I suppose it was probably just a spur of the moment thing for him.

Edited to add: even with the expensive bottle, he'd be using a couple of pounds worth of it max of it was just the once. Surely you've spent that on a treat or toy on occasion?

Both of mine were runners and had selective hearing at that age, I used a chart for rewards, it worked occasionally.
They're older.now, they chilled,too bloody chilled sometimes.

.I remember my poor mum who often chased me and my younger sister, 2 year age gap, when there is two, they egg each other on.
Fun memories.

Yes this was my objection!

@Thatsalineallright It isn’t harmful but it’s very expensive, especially DS’s (he has a special one due to eczema.)

Depends what sunscreen you use. If it's £30 a bottle then it's a no!

I really do get your frustration, but perhaps with some things it's worth just letting the child decide? Sun cream isn't harmful. If he wants to practice putting it on, why not?

We all have to say no so often to our kids for their own health and safety. When they have a quirky idea that isn't dangerous or harmful then maybe take the opportunity to say yes for a change?

If you have to resort to shouting to get them to listen to you, yes you have lost control and they know it too.

If you want your children to listen to you, you need to

a) stay calm and speak in a firm calm voice. Don't repeat yourself, plead, cajoyle, bribe or negotiate. Say it like you mean it and then follow through. For example, if you say we're getting in the car now and they ignore/run off - don't shout, pick them up one at a time and strap them into the car.

b) be consistent. If you give in/give way sometimes because you're tired/haven't got the energy, they will always push their luck in the hope you'll give in. You have to follow through with making them do what you want them to do, every time. So essentially, pick your battles but make sure you win them. For example, you can't force a child to go to sleep but you can expect them to stay in bed and put them back there if they get up. You can't force them to eat but you can say no snacks/treats if they haven't eaten their dinner etc

It will take time but they will learn, if you are consistent, that when mum says something, she means it. So if they misbehave in the shop, we're going straight home and we won't have any treats. If you can involve them in a task eg can you find me 3 carrots? Help me pick out some apples and put them in this bag, keep them busy and engaged they'll be less likely to misbehave. Likewise walking to and from school - look out for birds, funny shaped clouds, dogs, swishy leaves on the trees - anything that keeps them chatting and walking. Use reins/wrist strap if necessary to keep them safe if they attempt to run off.