You might find some possibilities in the http://www.flyertalk.com/forum/marri...ides-kids.html thread.

And in the Orlando area, the Marriott World Center has a couple of pools. The largest of them has slides and waterfalls. Though per the hotel's website: "Our Falls Pool ("our signature" large pool) will be closed from August 1 – November 30, 2012 for a renovation which will include the addition of 3 new waterslides and a poolside bar and grill." So it will soon have a bunch of waterslides added.