I went to Atlanta last year, hit the World of Coke, Aquarium, and the Center for Puppetry Arts among other spots. If you have any questions. I liked the WOC and I don't think I paid that much to get in, it was clean and fun, but nothing ground breaking. The Club Cool room was the best part... a lot of the other stuff is like EXTREME marketing... "Coke is a very important part of everyones life?... RIGHT?"
The Puppetry Arts place is a bit away from the downtown stuff, but worth the trip if you're a huge Muppet fan, but isn't very big and you can get through it rather quickly even if you take your time.
I also went to the Civil Rights Museum which was very educational and moving, but is def a bit of a downer, but if that is something you were interested in I would highly recommend it.
The Aquarium is AMAZING def the biggest Aquarium outside of SeaWorld I've ever been too... highly recommended tons to see and lots of shows.