The water parks can be good fun, and do have more to offer than the hotel pools. Getting around them in a chair isn't too bad, though there are more limits on what you can get to, than there are in the theme parks. Most of the slides are not accessible, though the family raft ride at Blizzard Beach, and the Crush 'n' Gusher at Typhoon Lagoon are.
To go on the family raft ride at BB, you can use the gondola car on the ski lift. As your husband won't be there to bring her chair back down, you would need to borrow one of their water chairs, leaving her chair at the bottom of the mountain. When you get to the top of the hill, and have got through the line ride, they will stop 2 rafts on the loading belt (like the moving walkways, but wider), putting you and your daughter in the second one. The water chair is then strapped onto the first raft, and sent down ahead of you. Once you get to the bottom of the ride, the chair should be waiting there for you. It's then just a short trundle back to the bottom of the ski lift for her chair.
Both of the lazy rivers have bump steps at at least one on the loading points, with an area to put the wheelchair out of the way. The two wave pools also have zero entry points, though she might find the one at BB easier, as there is a hard paved entry point, with a wall on one side and a grab rail in the other. Also, the BB waves are gentle bobbers, rather than TL's bigger waves. They have a number of rings in the BB wave pool, but there is rather a lot of competition for them.
The water parks can get busy, but like all the others, they have quieter times. Don't go to them on the weekends, as a lot of local families visit them then. Also, if you can plan your holiday so it's not during school holidays, you'll have much smaller crowds everywhere, though I know that's not always possible. We've found that the water parks are often quieter on overcast days, but you would have to be prepared to get out of the water quickly if there was a storm coming. How well could she handle such a sudden park closure?
Completely random tip here, but we always wear old T-shirts over our swim things, to reduce the risk of sunburn. Waterproof suncream is another must!
Good luck and have a great trip
