I've been for one day while on a cruise. We actually booked our room at the Comfort Suites, right next door to the Atlantis, which is much cheaper but gives the same access to pool facilities.
The water area is awesome. I was with 2 15 years olds, so my perspective is a little different that your age of children. There appeared to be lots of fun things for smaller children too.
The food is pricy, though we found a family hamburger pack offer, which was very reasonable: 4 burgers, 2 large orders of fries and 4 sodas for $25. This was out by the pool.
My daughter keeps wanting to go back to stay there.