Seeking expert testimony is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
I believe that i can help with this situation.
There is absolutely no way to please everyone.
You are the parent and you need not worry because you cannot do the impossible.
Make your plans, set a schedule for when everyone will be there and when they will not.
Minimize or eliminate overlapping times when your two incompatible daughters will be there and give them both the same schedule which will speak for itself.
This is the best that you can do.
This is a simple but effective solution and is probably the best and least problematic one.
If any of them cannot abide by this fair and compromising solution then they will have to be on their own, and you can tell them that they are denying their children the luxury of family relationships for their children, and this is a very severe penalty for innocent children.
You really have no other choice but to make the best plan, ask for peaceful cooperation, and not be pressured into taking sides or being involved in someone else's emotional problems.
I shall keep you in my prayers.
Elliott, MAE, LPCC, NCC, CCMHC
You are most welcome.
May God bless you and your family and bring them the gift of unity and forgiveness.