I understand your concern regarding the water park. I initiated a thread on this last summer when I first started posting to this board.
It seems like the water parks are the last area without across the board accomodations for the disabled. My wife and I visited Typhoon Lagoon last fall (without our kids - while I was at a professional convention!), and we saw twin girls about 13, both in wheelchairs. They had gotten a trip through the Give the Kids the World organization. Their mother was upset in that there was no way to get the girls up the stairs, ramps to the tops of the waterslides. I ended up carrying them up so they could ride (my poor back!) Mom was pleased with every other area at WDW, though.
My two sons, age 4 and 2/3 triplets, have CP, and ambulate with some difficulty with aids. I understand the frustration with the kids wanting to do the slides, with no lift feature to get them to the top of the ride. Some on this board had commented that many of the disabled visitors would not be able to safely swim or ride a slide, so the costs associated with providing accessibility for those others, like my kids, would be excessive.
I think that if someone can swim, with or without aids, they can enjoy several features of the water parks, including the swimming areas, the leisurely tube rides, and maybe even the wavepool. We're leaving for WDW this week, and we are not going to the water parks. When our boys are older and want to go, we will probably give it a try, and I'll take by lifting belt to carry them up the mountain!
I hope this can stimulate some more discussion about accessibility and the water parks.