Renee,
Am writing this from a grandparent view (I have two and they are the only ones on both sides).
When you have children they are yours not your parents so set boundaries especially at bedtime as that is a very special time to have together (it also helps your child to settle quicker). Sure they may feel hurt (or insulted) but you are the one who will have to deal with an unsettled child, no matter how good he is now, so a routine is helpful.
You also need time together as a family and not just a week night.
We have boundaries with the boys for which I am glad as we all know where we stand. Sure, we sometimes break them but it easy for the parents to tell us when we have due to these.
As for when you have your next, yes give them the later date. I never wanted to know the exact date as I wanted the GKs to be a surprise.
All the best as you deal with in-laws but remember this is now your family.