Hi Kim,
My family loves a visit to a Disney Water Park. We go to one on almost every trip. We love
Disney's Typhoon Lagoon Water Park, with its lush, tropical theme and fun attractions.
We typically arrive at a Disney Water Park right at opening time, and stay until about mid-afternoon. We try to ride the more popular attractions first, because just like at the Disney theme parks, they will build lines as the day goes on. Once we have had our fill of the more thrilling attractions, we head to the lazy river or wave pool and relax until we are ready to head back to our resort.
At Disney's Typhoon Lagoon Water Park, we really enjoy the waterslides that use a tube. These are Keelhaul Falls, Mayday Falls, and Gangplank Falls. Gangplank Falls is a raft ride for the whole family, which is really fun. Although none of these have a height requirement, Keelhaul Falls and Mayday Falls are both single-rider slides, so your little one would need to be okay with going by herself.
Your older son might enjoy both the Shark Reef and Crush 'n' Gusher. For the Shark Reef, you need to be able to swim across a lagoon, which it sounds like will be no problem for him. Crush 'n' Gusher is a really cool ride which is like a roller coaster - you go both up and down! While he enjoys these attractions with one adult, your little one could be playing with the other adult at Ketchakiddee Creek, which is a great water play area for small children. If you spend the rest of your day with your family all together at the Typhoon Lagoon Surf Pool and floating around the wonderful lazy river Castaway Creek, you have spend my family's perfect day at Disney's Typhoon Lagoon Water Park.
I hope these thoughts are helpful for you, Kim. Please do not hesitate to ask if you have any further questions!