My A was with my SIL. BW and I have talked to our MC a LOT about what to do at family events (we have two weddings, and two bridal showers this summer).
I wanted to talk to my BIL and AP before seeing them in public. Our MC doesn't really think that is necessary. Sure -- if BIL is ready to talk, we should talk. But if not, then we are going to show up, keep our distance, and get on with our lives.
Family is going to take their cue from your BS. Hopefully. My first family gathering (without BIL and AP) was Thanksgiving. I was a wreck. It turned out fine. Actually, it gave us some hope that someday, things would be OK.
Good luck to you both.