We did our rehearsal dinner at Nonnah's. It turned out well, but the venue may be too small for a party of your size. If you have the option hosting somewhere and having someone cater it, you should look into Spotted Salamander Catering. I've seen their information on the All Local Farmer's Market website, and the food sounds really great.
Farmer's Market Cafe
63 Chattahoochee St, Helen, GA 30545
There is a nascent related thread here: http://chowhound.chow.com/topics/708628?tag=main_body;topic-708628. One place I am considering is 300 Senate, with the in-house catering by Dupre Catering: http://www.duprecatering.com/300.html