Atlantis in the Bahamas. We went with our 2.5 year old in Feb and she's still talking about it, from morning to night. It has a lot of different pools, most with zero entry and including two kid pools and a splash climbing thing and smaller slides, lazy river, etc. Plus if you take turns watching the kids, there's grown up slides and a current river. Huge outdoor aquariums, plus a glass tunnel through a lagoon that you can walk through, and two of the water slides go through a shark tank. The bigger rides have a strict 48 inch requirement. It's expensive. Mostly the cost of food kills you, but there are ways to do it more cheaply. But it was a crazy good time. We'll definitely be back. Another recomendation is Rose Hall Hilton in Jamaica. Much cheaper, but still very plush, your drinks and food are included, and they have a small water park that includes a fabulous lazy river, zero entry pool, and a couple of slides right across from the beach, so very good set up to go back-and-forth with kids. There's also a small playground. We loved that one too and much more affordable. You can usually find specials for it on travelzoo.com