To ask how on earth you ‘slow down’?

You can say no. As a single mom, you're it for your kids and you need to put your health and welfare ahead of martyring yourself to the demands of friends and family who may have help with their families that you don't. Tell them you have to slow down and you are only going to be able to do things 2 weekends a month. You need boundaries for your health here.

You're running yourself into the ground being a people pleaser. Your mom noticed. What will happen if you get really sick?

Have you asked the kids what they’d want to do at the weekend? That’d be my starting point, as it sounds like they never get time at home just to mooch about. I also protect time, so we’re always at home on Sunday afternoons barring a family birthday or other important event.

If I were you, be honest with your friends and family that you’re going to be less available for a few months to catch your breath, and see how you all feel when you’re not trying to tick all the boxes you have got in your head that must be fulfilled each weekend.

...otherwise what's the point of weekends...

The point of weekends is to sit around in your pajamas and let the kids have some downtime too. It's not good for them to be constantly entertained or whisked off to scheduled activities. They need time to just live in their own heads.

Double up on the play dates. If DS1 has a friend over, do the same for DS2.
Say no to one in every 3 or 4 invites from each group of people. It IS ok to say no. It IS ok to have plans revolving around sitting at home. It IS ok to put you first.

This is crazy. Just plan to stay home with your kids every Sunday. You are lucky to have so many friends and family but just make plans with them slightly less often.

Do your shopping for gifts and food online. Kids don't need playdates, sleepovers and days out every weekend - aim for once a month instead. Catch up lunch with family one weekend day and have a lazy/home day next day. You don't have to socialise every weekend either. You can cut back and slow down, you just need to learn to say no! Why not invite a friend over for a takeaway and a bottle of wine in the evening instead?

If I don't want to accept an invitation because I prefer a chilled home day, I just say I have plans that day and suggest we meet the following weekend. It's not a lie - I do have plans and they involve being on the sofa, playing games with my kids and pottering around the house. Would something like that work for you? I think you should look at why you say yes to everyone and overcommit yourself. If you can identify the reasons it might help you to change. For example, do you feel restless/sad if you stop and sit down? Do you fear people will stop wanting to see you altogether if you decline them once?

Plan down time. Have a play date but when it's their turn go for a pub lunch, soak in a bath, read a book etc whatever suits you

Cut down on the playdates, you can still do them but every other weekend for example. You don’t need to do a day trip to London, a half day out there lies a chilled afternoon would be fine. It must be tiring for your kids too if they’re in childcare every day after school and in holidays, sometime a relaxed day or afternoon in is good for everyone.

The answer to that is "really looking forward to some chill time! Coffee and a book in the garden!".

People will understand. Kids benefit from nothing days sometimes too. If that's what you need, that's what you need.

If it makes you feel better, plan it in. On the calendar, see X here, kids have Y here, this Sunday is for chill time.

Teach your kids to slow down too or they'll think they should never be stopping as well.

And I imagine some of this stuff is eating into your budget big time.

What others said. There are probably extro-extroverts who get their energy from having non stop chaos and buzz in their lives/homes, but most people, adults and children, need some downtime. I'm not a single parent or a FT worker and my kids are not at a sleepover, zoo or museum every weekend. Look at what you do on a typical weekend and halve it.

Bloody hell, I'm tired out reading your post!!

you are putting too much pressure on yourself to do so much with/for your kids.

its lovely, but you're going to burn out/make yourself ill. Then you'll have Big Problems!! I think you know that though.

i think all you can do is accept that you can't (no one can) do everything as often as you are. Don't stop anything in particular, just the frequency of each thing. You're packing too many things in!! It's not necessary to do them as frequently as you are!

How do your kids cope with so little 'down' tine? Kids actually NEED the opportunity to get a bit bored & have to make their own fun.

How did the holiday club work out? Have you thought about paying a teenager to come to your house? You're honestly a lot of the time if they need you & if they're older 15/16 can cope while you're out on visits.(doesn't help much either you being too busy, but is cheaper & would give your kids some diwn time at home, that's what I hated most when I had to go to childcare in the school holidays. No time At Home to chill)

Use family as babysitting to get some time to yourself too.

Can you make some meetups more regular, e.g., last Saturday of the month, so you know you'll be meeting, and just explain you're too busy with the kids right now to be spontaneous

Stop the days out. I used to feel like the kids needed them, wheras actually they needed me. They needed me to be present with whatever they were doing. A day playing games at home and a walk to the park is just as good to them as a day out in London.

Could you do an open house type thing regularly? For example, say you'll be doing a simple brunch (fruit, croissants, juice) from 10-12 and people can come if they want to. A friend started doing this and it took a while to establish but it's quite fun.

It's perfectly acceptable to say things have been hectic at work and you really need a chilled weekend. Anyone who has experienced juggling work with young DC will understand. If they don't get it, so what? If they're a decent friend they won't want you running yourself ragged.

A full day off every fortnight minimum. Every weekend doesn't have to be full on.

I know it's difficult because you feel you are pulled in all directions, but for me, the first thing to go would be sleepovers and days out. If the kids have been in a holiday club all week, they almost certainly don't need these as well.

A duvet day at home, with a movie and popcorn, or a trip to a park, or a walk in the woods would be just as good. No kid needs to be constantly on the go, it's exhausting for them as well as you. It's ok for them to just mill about at home getting bored too, if that's all you've got the time/energy for.

Playdates for DC1 & 2 at the same time. No sleepovers unless it's a real big treat, like a birthday, and even then better not. They get worse as DC get older, up really late, then one wakes the rest up early and then they're all grumpy for the whole of Sunday.
Combine outings with other things, like seeing friends and family. Make some outings much more low-key - trip to local park or woods, get an ice cream or take a small picnic, meet family or friends there.
Driving into London sounds a nightmare, why would you do that to yourself? If you must visit for museums etc, get the train/tube/bus. But that sort of trip doesn't need to be often. Have some chill time at home - designate part of each weekend, a morning or afternoon, to relax at home. It's fine for kids to watch something in their PJs till lunchtime if the rest of the weekend is busy.
Do what you can online - birthday presents, food shop etc.
You don't have to arrange entertainment for your DC for the whole time.

Your kids do not need you to drive to London for a day out. They would be more than happy chilling at home. You say you’ve already done a sleepover?

You will burn yourself out if you continue like this.

You don't have to facilitate playdates every weekend, surely? Presumably the kids see their friends at school during the week.

We tend to save things like the Zoo, Museums, trips into London etc for the school holidays. We rarely do a full day trip in term time, usually just stuff like the park or cinema on a weekend in term time. I think it's important for DC to have downtime and mine tend to need at least half a day at the weekend just to chill.

I do pretty much all shopping online, Amazon Prime has saved me wasting precious time trawling round the shops looking for last minute birthday presents more times than I can count.

I think most of us with young children (especially those of us who have DC with SEN) don't necessarily see our friends as often as we'd like. I understand what you're saying about it not being fair to you if your social life was the thing you cut back on, but something has to give and I think it's pretty normal if you're exhausted from work and parenting to say no to some social stuff.