Okay, so when I am invited to Thanksgiving, B Days, and Christmas etc, just be friendly..
Mach, that's up to what would feel good to you. I don't do Christmas with my ex. This year, the kids will spend the early part of Christmas vacation and Christmas Eve at mom's, and Christmas Day and the later part of Christmas vacation at dad's. My kids look forward to Christmas with me because it normally means a trip to find and chop down a treee plus a vacation--my ex was allergic to road trips, so that's uniquely me. I'm curious if a combined Christmas is a tradition you plan to continue once you have new partners. If not, consider what tradition(s) you want to begin around the holiday season?
You might ask, "Doesn't this contradict my XW being a friend?!" Well, I don't do Christmas Day with friends. For me, the holiday is about spending time with my close family. To each their own.
If you're struggling, stronger boundaries, to begin with, may be helpful.