To not get DC a snack

I'd work on gearing the 4 year old in their own room and having the bedroom open and the 7 year old sitting outside it while you do that

If you can sort out the youngest it gives you more time to then work on the oldest

Okay so can you work towards a situation where you can be in and out of his room at bedtime while putting sibling to bed? All doors open so he can hear your voice, could he be snuggling in bed while you are in the next room reading to younger one but pausing every 2-3mins and coming into him to reassure?

The answer here would be a firm no to all of that rubbish.

Sorry to disagree but I suspect this absolutely IS part of their autism.

Both of my boys are autistic and I had hell with sleep with both of them when babies and some issues lasted longer - they’re 11 & 6 now.

But that doesn’t mean you can’t make a difference.

Also, mine have ALWAYS needed less sleep than other children.

The 6yo goes down between 9.30 & 10.00 and wakes at 7. An earlier bed time results in absolute chaos.

If your kids need less sleep then put them down later.

Use a visual timetable, use objects of reference, you also need to get your 7yo’s anxiety under control. Is he having ELSA? Seeing a therapist?

You cannot separate this from autism - autism is pervasive and affects every part of a person’s life. Strategies that work for NT children will not necessarily work and can be harmful. You need a proper plan and to start over.

Will your 7 yo sit on the landing outside the 4 yo room while you put them to bed?

Your kids are completely taking the piss out of you. Find a backbone and be strict with them. Sit them down and draw a list up on a big sheet of paper. Bath. Story. Bed. That is it. Pin it up on the wall and keep reminding them of the new mummy and what's going to happen tonight. Tell them there will be NO more up and down and you will be returning them to bed with No speaking atall. Keep doing this they get the message. And they will believe me. Also watch the 3 day nanny back to bed routine on you tube. Stick to it. Do not talk. Keep returning to bed. Do it for them aswell as yourself. No one needs this rigmarole at night time there's no need for it. Do it tonight.

Also in that can you and 7yr old almost put younger sibling to bed in their own room, together? Can they be your helper, then you and 7yr old leave younger one in bed to go to sleep and go and have a story in another room?

How does your 7yr old cope with sch? Are you doing anything to work on the not being left alone issue eg gradual retreat techniques? I appreciate it may be down to his autism but long term its not going to be manageable in his life to never EVER be alone - do you have to accompany him to the toilet every single time? Does someone at sch? If not, then he can be alone briefly, and is that something you can then build on?

I would refuse to go up to them and if they came down asking for things tell them no tv for the next day if they come down again and stick to it - or no games or no phone or whatever they will really want.

Good on you for not blaming autism. Too many things are blamed on X or Y.. Sure, there's a reason why Billy punched Jill in the face, but there should be zero tolerance on doing it in the first place.

Ah, my elder daughter- the one I had to hold her hand and lay on the floor for 15mins every night for her to go to sleep- she is Autistic and has ADHd

The OP is doing what I used to do. Put to bed, leave, they call out, I go back, leave again, repeat until I fall into bed.

What 'treat' in the school holidays is coming up, say a day out. Make it conditional on none of this nonsense, be strong.

They crossed the line of 'them taking the piss' a long, long time ago.

That's a lot of drinking just before bed too. Of course they'll then need to get up for a wee. That can be managed better.

Your eldest is getting close to an age where he should not be sharing with an opposite sex sibling, do you have room to give them their own bedroom? This might help because the younger one should go to be earlier and it would stop her winding him up if she carries on.

This. I think you may have to find your stern face and shouty voice, and scare the living shit out of them if they get out of bed once more.

My daughter went through a stage of declaring she was so so hungry after bedtime at around 4 years old. What I did was only offer a specific type of bread, that she didn't like but would eat if she was incredibly hungry. This stopped her asking if she was just delaying bedtime but on the rare occasion that she actually was hungry, because she hadn't eaten well earlier, then she'd eat the bread.

I assume they’re sharing a room currently - any way you can separate them?

I agree with an earlier dinner, then a boring snack before bed (weetabix / toast / porridge / banana).

and then maybe it’s time for some tough love, they’re not little babies and it does sound like they’re taking you for a ride a bit.

OP who is in charge here? Your kids sound so badly behaved jumping about on beds attacking each other at bedtime 😬 they are probably really chronically overtired too, going to sleep so late, which probably then doesn't help the next day.
Is this a pattern repeated in the day where they don't really listen to you /follow instructions? Maybe its worth reading some parenting books /booking a course and seeing if you can change the dynamic in your home to get yourself back in charge?
A pp made a good suggestion of getting the younger to bed half an hour earlier. 7yr old could snuggle in your bed with a book /quiet toy (calm tv show on a tablet even?) while you read to and settle the younger who then has 20-30 min to fall asleep without the older one there distracting. You can then have some quality time with the older, read a book together in low light, before sneaking them in to bed.

Mine were exactly the same OP. It used to drive me absolutely batty, and then when they'd finally stopped fannying about I'd feel awful because it used to make me so angry.

Hang tight, they grow out of it by about 14

Yikes. Shocked at all these responses about serving supper, cake or icecream before bed?? My 5 year old gets her dinner at 5:15....... and then breakfast at 6:30 the next morning. She doesn't even have a pudding 😬 anything sweet or sugary is consumed pre 3pm to avoid erratic behaviour at bedtime! She's usually asleep by 7:30. However I can remember being a biscuit scoffer pre bedtime and dear mother would send us to bed with a glass of cola 😱 my brother and I still cringe about that now!

You're giving them dinner too late, and you don't have a proper bedtime routine.
Therefore they just aren't ready for sleep.

Better would be dinner at 5.30, followed by a short period of play before a bath at 6.30/7. Then teeth, drink of water, read them a few stories in bed before lights out at e.g. 7.30/8pm. Audio books don't have the same benefits as reading actual books and may be keeping them awake. Put a water bottle next to their bed and let them go to the loo if they need it, but don't engage too much and no snacks.