I believe High Cotton has a room (or two) that accomodate large parties. High Cotton is to die for...especially the creme brulee!
I believe Devereaux's has a private room as well but it can't do 50 seated, just standing. Lazy Goat has private rooms as well, plus a patio that can do 50 seated if you guys are getting married in temperate weather. There's the Soby's Apartment as well but I imagine that could get pricey.
Ford's Oyster House may be able to accomdate 50 and it would probably be the cheapest option. And more laid back. Depends on the vibe you were going for.
For Greer, Bin 112 and The Strip Club 104 (it's a steak house...LOL) in downtown both have private rooms but I'm not sure if they can fit 50 people. The chef there is super awesome.
Good luck!