Hi belleofabride!! What do you mean when you say post wedding brunch? Do you mean as a reception or do you mean the morning after all the wedding festivities?
If I'm ever looking for a restaurant, the first place I go is Yelp. It's got a lot of filters and can really help me figure out what I want and what I need. I suggest conducting your own search on there, but I did one with the parameters that I thought would work best for you and came up with a couple of options. There's South City Kitchen and The Flying Biscuit Cafe in Midtown and Egg Harbor Cafe and R Thomas Deluxe Grill in Buckhead, so maybe google those places and see if they pique your interest.
I recommend Murphy's in the highlands. Whenever I am in the city, this is my go-to location. They have really good food and could offer a prefix menu. The current prefix menu doesn't have my faves but, I would suggest you call them to make substitutions if you want. The price is about 30 pp. Another place would be South City Kitchen because their food is delicious as well. Both places offer private dining