To get so stressed about my kids’ car behaviour

I think you need to absolutely lose it at them. Explain clearly at the start of every journey that any unbuckling will result on consequences and mean it. I would plan a fun activity such as soft play, swimming or trampoline, that can be paid for at the door. If they muck about on the way, go straight home and they have lost their chance. If it happens on the way home, they have no screens for the rest of the day, no pudding, or whateverit is that motivates them. It's not just annoying, it could be fatal.

I did the nuclear option 30 odd years ago..again quite a rural location, mid winter, very few cars...pulled in a lay by, shouted at them to get out..put them on the grass..told them' That was it, I was done, I was leaving them', I went to get in the car to drive off..they realised I 'meant' it..started screaming( probably in fear), I told them to get in, they did very quickly....so I shouted again that if they ever dared to get out of seats or fight, I wouldn't let them get back in, that would be it! We had a very quiet drive home! Never remotely tried it again.

I know its frowned upon parenting these days but just very occasionally they need to be afraid. Humans usually avoid what frightens them.

Would carrying out a major threat work?

Only the other day dd was talking about the day she cancelled a planned day out to a theme park, because Gds was being (as she put it at the time) ‘a little shit’.

He was no more than 5. She had threatened it, but he evidently thought she was bluffing - until it happened.

He’s now 10 and she said he still remembers that, and now knows that pushing it too far will most certainly have Consequences with a capital C.

So the issue is only really your 5YO? The 3YO stays buckled in the impact shield seat if left to their own devices and it’s the eldest doing the unbuckling? Firstly I’d put the youngest in the front to protect him from his brother. Push the passenger seat all the way back and check the car seat installation guide and car manual re the airbag since the seat is forward facing. Then you need big consequences- properly tell him off (it’s one of the rare occasions where shouting is actually called for) and if he doesn’t immediately rebuckle himself then cancel the day out if it’s the on the way there or maybe he loses TV and has a time out instead when you get home if it’s on your return journey. Do that in conjunction with a reward e.g. a sticker chart or a treat when he gets home for staying sat nicely. Hopefully you’ll get through to him. I would start on a day where the plan is stuff they’ll really want to do e.g. soft play then home to watch a film so you have some leverage.

Your blasé attitude is absolutely alarming. Someone will end up dead. Control them or stop taking them in the car FFS.

You said none of the consequences have worked, they obviously weren't severe enough.

Absolutely don't do this

You can get seat belt clip covers that can only be undone if you poke something into the slot.

They're classed as unsafe in an emergency because you can't just push the button to release but they're much safer than kids flying through windows or causing a distraction plus in a true emergency it is likelt the seat belt would be cut anyway.

They have saved our sanity when we've had multiple kids in the car because even on their best behaviour sometimes they unclip the wrong person's seatbelt by accident.

Sitting on the front in a suitable car seat is infinitely safer than having a child unrestrained in the car.

OP, my grandchildren are slightly older than your DC but they sit separately, eldest in the front, youngest in the back, no arguments. There are no problems now with their behaviour whereas at one point they were feral. Their parents would have to stop the car to refasten them in, and eventually stopped taking them out together. They arranged a day out and really bigged it up, then turned the car around as soon as they started playing up. The DC got the message!

Why not tell them to bloody well stop it, and if they don't, there will be consequences? Don't let them get away with it. Discipline is what is required.

Gorilla tape?

There is no need for a seat buckle, they aren't safe and delay getting your child out in an accident.

What does need to be addressed is your 5 year olds behaviour. They are old enough to know what they are doing. Your 3 year old is not at fault here even if they are instigating the older one to misbehave. I also live rurally you absolutely can stop in a pull in, someone's long driveway or a farmers field entrance if need be. You sound like you are either at the end of your tether or quite passive.

I've seen far too many accidents in my career in haulage to be passive about road safety.

My husband has made wooden barriers that slot down car seats...they can't see each other with the barrier up. Has reduced the fallings out, but does look ridiculous.

Just threaten them with withdrawing anything they really like for a time if they do not comply - and be ready to carry it through if they don't!!

Mine have never unstrapped but we frequently get a lot of shouting when they're together. A lot of competing SEN difficulties that boil over when together in the car. We find Simon Says very successful for a variety of situations. I'm not saying it wil work but it's worth a shot for the moments you can see things about to escalate.

I gwt what you mean about windy roads (I'm Cornish) however if it is your child's life at risk then I would be stopping until they are buckled back in. There is sometimes a gateway to pull into but no matter what I would be stopping.

I drove mine to a police station once after ds unbuckled his seat belt and they starting hitting eachother.

The civion the front desk (who was dressed a bit like a police officer) came out and gave them an absolute bollocking. It absolutely did the job and they never messed with their belts again.

I think this is a good tactic tbh. They have to understand the safety consequences. And I bet if you did drive them into a station they copper behind the counter would willingly play along.

tell them - Let’s go to the park. If you unstrap your seat belt we will come home .

simple clear unequivocal language and consequence explained.

if they unstrap - you pull over - you restrap them on and tell them off for undoing the seat belt:

then you drive home. No trip to the park.

should they unstrap again you repeat as many times as you need to and get them home.

The. You firmly tell them because you instrepped your seat belt er did not go to the park.

you have to be the adult. You have to parent. You have to show them this is a completely inflexible boundary.

a few missed trips of fun - they will get the message. And understand that seat belts are non negotiable.

I do that when I share with my kids 🤣

You stop, strap them in, turn around and go home. At home they are not given any treats, it's quiet play or bed. It's that simple.

They clearly have no respect for boundaries and despite what you say, I suspect they are not as well behaved as you think. It just isn't as serious so you won't notice it.

I was going to suggest taking them to a police car safety thing or a pcso drop in (there’s one at library and village hall near me every month) and get them to explain to children to reinforce how dangerous it is.
I’d probably limit trips to essential only.
Before trips set out expectations.
I do think safety issues like this justify an extremely angry reaction so they know they have crossed a huge line. Not a wishy washy you need to put on your seatbelt darling.

I had three autistic boys. I tolerated a lot but never safety issues like this. I’d pull over each time.

Not in the front.

Carrot and stick. I hate screens, but I think in this case I would let them have screens in the car and any kid that acts up has it removed.

I also hate shouting and have only really let rip once and it was in the car. DC have not really messed about in the car since. I think it was so effective as I really don't shout (get plenty of other things wrong, so this isn't a boast), so it was a shock factor.

Can you plan trips so you know where the neatest safe places for pulling over are? Then use them. Give them a proper, firm, telling off.

The next few essential trips - leave early. Like, REALLY early. "Ws'll go for cake first if theres time, but Im not going to drive the car if youre not sitting properly as it is dangerous".
The trips for something nice can be ditched. Trips home - even if for dinner- will be paused at first misdemeanor, then whenever they so much as squeak or wriggle therafter. A proper telling off each time.