atlanta/vinings: great for a group?
Although I've never had dinner there, I bet a fun place for a group (if you call ahead) would be Muss and Turners. Their dinner menu looks really good.
You could also do South City Kitchen in Smyrna, although it tends to be inconsistent I think.
Obviously lots of great group options if you want to venture south...Eclipse di Luna, Pura Vida, Baraonda...
My first idea was to mention Muss and Turner's...although my only concern there would be the space for a party of 15. Outside of that, it's a quirky place that is now considering itself a "gastropub" with an assortment of sandwiches, small plates, and specials that would most likely please a wide array of tastes. I always enjoy my meals there...and they have an eclectic wine and beer selection.
Outside of that, many of the places in Vinings are seemingly inconsistent. South City Kitchen is sometimes good, sometimes not. Blackstone is overpriced for steaks and such. I have not been to SOHO so cannot speak on the food there.
There is a new seafood place called C&S Oyster Bar (not just oysters, however)...and I have heard mixed reviews of it, as well.
As others have said, if you're willing to venture out of Vinings..it opens up a whole new set of choices...