Surely any child will be asleep at that time anyway? If not in bed then on a couple of chairs pushed together.
Is it in a hotel OP? Or a private home? I'm just wondering whether you could sell this as a sleepover for your step children and your family's children?
I know that is a lot to ask of your neighbours and means in the morning you will have a house full of children but it might be a solution.
Say there will be pizza (actually whatever the cousins' favourite food) and a movie in your house at 11 for any children who want it and they can bring sleeping bags.
I may be influenced by my own experiences as a child at weddings. Particularly my uncle and aunts, I'll post it here in the hopes that it will amuse you.
So I was 10 and a bridesmaid, it was March and I was in a short sleeved cotton dress with American tan tights and those silver plastic sandals that you wore for dancing in the 1970s. Obviously the shoes were new.
My mum didn't do breakfasts so we had not eaten before the wedding, we drove to my soon to be aunt's house and waited there for everyone to be ready and set off, I was put in a taxi with my new aunt's mother.
Then there was the wedding, which being RC meant a long mass (not quite Polish length) then photos outside which was freezing and then to the Town Hall for the bun fight.
We ate at about 3 pm, so I'd been frozen and starved.
We went back to my grandparents house for a cup of tea and some spice cake and for people to get changed. I can't remember but I don't think my grandparents were going to the evening do. I was a bridesmaid so I wasn't allowed to get changed (ie my mother wanted everyone to see me in the dress) and the plastic sandals were cutting my feet to ribbons. And my brother wouldn't bloody shut up that I had had wine with communion and he only got the host.
So we go, as a family, to the evening do. Me still in the dress and sandals, still no jacket or wrap and by this time it was dark.
Now my aunt and uncle met when she was working the summer between uni years at my uncle's workplace. He was a psychiatric nurse. The evening do was at the social club where he worked.
So a social club at the local psychiatric hospital which had been a Victorian asylum.
Have you ever tried calling a taxi to an asylum at 2.00am? This was the 1970s so there was still a lot of stigma about mental health.
My parents didn't wait until 2.00am to phone, they had been phoning different companies for an hour. They all said the same, they were on their way and then didn't turn up.
My dad said we might as well start walking.
I nearly cried, my feet were bleeding by this time, it had gone from cold to freezing and I was still in the bloody dress with the now literally bloody sandals. I think my dad lent me his jacket at this point.
As we got to the main gate a cab pulled up, I have never been so grateful to get in to a cab.
We stayed over at my grandparents and the next day I found out my mum had forgotten to pack any shoes for me.