There’s no fucking way I’d take part. Let her know now before the wedding that you won’t put up with her family forcing you into anything (imagine how worse it will get). I do like the idea of screaming crazy shit from the bedroom, “You are so much tighter than your mom HOLY SHIT! Choke me like your grandma did! Where’s your grandpa? He’s got a big dick, I saw it in the john at the restaurant, it’s huge! Get his old dick in here!!” And calling out the names of your gf family members. When you come out of the room give everyone big sloppy wet kisses and say, “How’s [wife name] taste? Who needs water when you have a squirt, am I right??”