Anonymous wrote:"Definitely a hotel this time, Mom. And remember I go back to work on Monday, so don't plan on seeing us after the pizza party (or whatever the last event is). I don't know what did or brother might have planned, but we need to regroup Sunday evening and won't be having anyone over for dinner."
Etc.
This is direct and to the point - keep your explanation simple and be ready to repeat it as needed. I have had parents pressure me and I found it easier to stick to what was best for my family by reminding myself I was standing up for my children. Yes, they need a bedtime and routine (a complaint I've heard too, OP) - and it's okay to say no to family when they want things that disrupt those needs. It's also okay to say no for yourself, though I know that can feel a lot harder to do.