Here's some of the places I'd list as options:
College Football hall of fame, Stone Mountain (Better at night with the laser show, also a little outside of the city), World of Coke, Georgia Aquarium, Centennial Olympic park, Westin Hotel (Go to the Bar at the top, it is a rotating restaurant, with a great view of the city, don't need to actually sit at the restaurant) , MLK historical sites are cool.