I would think more than a cruise would, but not having been on a cruise in quite a while, I cannot say that for sure.
But yes, there is lots to do. The aquarium, if you can call it that, is amazing. You can spend hours and multiple visits there. Feeding time is entertaining. The pools and attached slides are fun for all ages, especially the one going through the shark tank.
There are lots of beach activities. Strolling through the marina viewing the yachts is nice. The water taxi ride over to Nassau is an adventure. The market is interesting. If I remember correctly, there are scheduled activities that both adults and children can participate. If not, adults can at least watch.
If you were staying a week, you would get bored I would think, but four days is a good timeframe.

Atlantis has a very nice web site: www.atlantis.com