Karen, I have been in sinular situations with my husband and his father and two brothers. I would go to an event like my brother in laws wedding and all the guys would be drinking heavily. Then begining of the party would be ok but by then end they would all be drunk and the fighting and crazy behavior would start. Like they would go into the bar after the wedding and get in a group fight with another bunch of drunks. Then there is blood and cops and craziness.
I have decided not to go to another event when all the "boys" got together to drink. I just won't go anymore, it is not worth it.
Your situation might not be so extream, and if you can really get away from the group it might be ok. But if it was me, I would skip the party. A night out with the girls or to a movie, would be better in my book. Good luck.