Hotels around perimeter center might be okay as well -- though Buckhead puts you closer to all your destinations.
We just went to the new World of Coke last week -- it was great. I was genuinely surprised. It is next to the aquarium, though if it was me, I wouldn't do them both on the same day -- if I could avoid it.
Do you know about the citypass that can save you money on admissions?
Visit 6 Atlanta attractions for just $64, a $113.93 value!
I don't know how old your grandkids are, but mine love the CNN studio tour. This too is right by the aquarium.
We have a baby Panda at the zoo as well.