I don't disagree that aquatica is a good choice for your family but they are quite strict with hight requirements as well. I would suggest that you take some time to get all of your kids in the water and work on the use of life jackets before your trip.
One of the main issue you may have is the climber is so large, it is tough to keep track of the kids. I have 2 and both are good swimmers (we did survival training when they were babies) I ended up following my almost 3 year old and letting my 5 year old go. There was no reasonable way to keep eyes on both kids at one time. The larger slides in the climber do empty out into a pool of water that is 42" deep and there is some current so having them in jackets might ease your mind a little. I remember thinking that if I thought I needed to see both kids at the same time while we were in the park, I would have been a nervous wreck!!!
On the other hand, the "tween" area at Blizzard Beach is much easier to see them, but the water is deeper and the jackets would still be necessary.