I couldn't read all of the posts, but here are my predictions:
1. It's going to be a disaster
2. The groom will be too busy to play
3. If the groom makes time to play, his new wife will be really pissed.
4. All of the relatives over the age of 40 are not only going to dislike this, but they will actually be angry with the groom.
5. Some of the monitary gifts will be lightened or removed entirely from the envelopes.
6. The newlyweds will have their first fight before they make love for the first time as husband and wife.
7. The band will have a lot of stress and possibly a fight.
8. The wife will be so pissed about how the evening went, she may convince him to give up music and settle down.
9. Someone's gear will be damaged or stolen.
10. Arguments will ensue as a result of # 9 and the band may possibly have a scene at the wedding or break up.
11. You will wish you listened to us and wish you didn't do it.
12. You get to listen to crappy "musicians" play music badly while you continuously pray that your gear is OK and not stolen.
13. The guests will think the groom is a tool for turning his wedding into a gig.
14. Number 13 will be felt more strongly by the bride's parents and sisters, especially the bride's father. Therefore, getting the look every time he goes to his in-laws' house.
Please. Do the world a favor and convince this knucklehead that this is a total disaster waiting to happen.