Hi Leo! Jump aboard. Sorry to hear about the sleep problems, you have my full empathies there. Keep sharing and we'll keep coming up with suggestions.......
Momma/Triplets, what a programme! I've only seen the first but OMG!
Triplets, I'm sorry to hear your bedtimes are so bad atm. I truly believe in consistency. If there are really clear markers then testing the boundaries won't be such fun.
I know the age difference is totally different but, my DT1 (awful sleeper) stopped waking in the night a few months ago after doing it for her whole life so far. She got to the point she would be beside my bed with a different problem every 10 minutes from about 1am onwards. I waited until I felt my strongest then one night I literally sat outside her room for about two hours and every time she opened the door I lifted her straight back into bed, said "no darling, its sleeptime". She screamed blue murder, almost made herself sick with upset but I had come to a point where it had to get better. She is sleeping beautifully. I know it was maybe cruel (she was horrendously upset) but for everyone in the family she had to go to bed and sleep.
Could you do similar? You'd need to be rested, strong, prepared not to shout or show your frustration at all, prepared for it not to change overnight. Lay the ground rules with him/them in advance, at a calm/happy time. Let them see you are smiley and happy about it (that baffles them and they realise their larking about is having no effect on you) and then repeat, repeat, repeat. Wait outside the room and go in and calmly go over it again "into bed now please", lights out. When you want to shout, find a way to stay happy (tickle/kiss them as you drag their bodies back into bed? Is that threat enough maybe for a 10yr old boy? ) Anything so they realise you will not be moved.
I'd start with continuing to put them up to bed yourself, once you have that working really well, you can think about moving on to 'allowing' them to do it themselves.
As Mars says, if you keep going like a broken record and they feel there is a benefit to following the rule it should come good.
They need to know that you are their ticket to good times. (Make that a promise not a threat.)
Often you have to go outwith the ususal for it to work. So, if they go to bed well tonight, tomorrow and friday, they could do something fab on Saturday. Then really do it, even if its something you normally would't allow.