Holy shit, one week at Atlantis? You must have some big $$$
But like everyone else said, Nasau is a shithole, the restaurants in Atlantis are fan-frickin-tastic.
Take some boat tours, do some snorkeling, basically just get as far away from the resort as you can and go visit some of the cool surrounding islands.
Chances are, if you go snorkeling, it`ll be at a small coral reef. It`s pretty nice.
Anyways... yeah... good stuff. Oh, and watch out for ants crawling in your food. I stayed at the Sheraton across from the Atlantis complex and it was dirty.
But since you`re staying in the complex itself, it`ll probably be pristine