I did the aqua park with the big inflatable floating equipment with my 2 kids and it was a lot of fun. I would recommend it. However, it depends in the ages of the kids. These things were much harder to climb than they look from a distance. A seven year old or younger would not be able to to much at all, because just getting to the first step would be a problem. 9 year olds and up, inlcuding teens, would have a blast. Make sure you take a water camera. The ship makes a beautiful background from the aqua park.
I did notice that RCL is putting in a new water park (Pirate's theme) but it is not listed as a shore excursion. This one looks better for little kids. Could it be that it is free ??? - seems hard to believe, I don't know why it is not listed as a shore excursion.
$15 per kid for 1 hour. worth it - especially since it was the first stop after sailing a day and a half. Everything else there was very expensive - $100 per jet ski and the same for parasailing. Save those activities for an island where you can deal directly with locals.