what is a mil? I've never heard of that.
I'm sorry you have such a hard time with that situation.
I agree, making two sets of plans is hard on you.
I'd stick with one plan. If they want to miss out on the party because of "mil" then it's their decision not yours.
They can continue to make plans with you aside from that if they want, but make it their problem not yours. And don't let them make you feel guilty for trying to include everyone. That is the right thing to do. You can't control their decision to exclude someone from their life. And they should feel bad for making it harder on you. So I say just keep on including everyone to ONE gathering, and if they can't make it then oh well. You can't eliminate a family member or whoever mil is just to make them happy. Then you are leaving out another person, mil. That's not fair. Then it IS your problem.
It is their choice to exclude mil not yours. Don't make it your problem.
Sounds like they need to work it out between them, not you. You are simply in the middle. Try to let them work it out without you. NOT YOUR PROBLEM. You obviously love and want to include both, but you can't fix the problem between them, they have to do that.
I have similar situations in my family. I think many do. My oldest sis and second oldest are such opposites that they just try to avoid each other as much as possible. BUt that doesn't mean I have to avoid either of them, or plan parties around their differences. I let them feel however they want with each other and I make my plans to include them both. It's their own loss if they let their differences interfere with being able to be with me and visit with me and my family. That is their decision to deal with. Why make it my problem?
It's hard at times though. When one talks pourly about the other in front of me. I hear both sides. And I think they both are acting childishly. This coming from me, their youngest sister of four. I sometimes feel like the only mature one. I've got to thank them though for showing me great examples of what not to be like! ;)
LIve and learn from those around us and it makes us better people. (tell them to grow up!) ;) xo