I had a similar situation where a "friend" of mine (who is slowly becoming not a friend) has no filter and I didn't want to worry the whole week that she was going to offend my family or my FI's. I made it even harder on myself by inviting her sister (as my photog) and from what I hear she's not too happy about that.
Honestly it came down to I wanted to have a good time and not have to worry the whole week about people fighting, being offended or people not having a good time.
You and your FI need to be happy and have a stress-free time!!