The Crowne Plaza hotel in Times Square has a pool in the health club, but they may not allow kids, it might just be for lap swimming.
Other cool elevators in the city include the Prada store in Soho and the Apple store on 59th St., they're only two stories each, but interesting in their own way. Agree on Marriott Marquis and Too of the Rock. Also don't miss the Roosevelt Island Tram. And of course the Intrepid.