Hello, Kevin! I'm so excited that you are considering a visit to the Disney Water Parks!
If your girls are adventurous, I'd suggest a visit to Disney's Blizzard Beach Water Park. It has the best thrill slides of the two parks, in my opinion. My favorite attraction in all of Walt Disney World is Summit Plummet. Your girls may be a bit young to really appreciate the thrill of dropping down this steep slope, but you can certainly try it!
Your girls might enjoy the
Toboggan Racers, where they can race to the bottom of Mount Gushmore on a gently sloped hill. The
Ski Patrol Training Camp is nearby, and offers a really neat ice balance course and mild-but-wild slides perfect for the 'big kid' age group.
If your girls prefer a milder slide experience, then Disney's Typhoon Lagoon Water Park may be the way to go. This park offers a nice assortment of family and individual tube slides, as well as the opportunity to snorkel with sharks, stingrays, and blue tangs at
Shark Reef at no additional cost.
Both of the Disney Water Parks offer plenty of shaded areas for lounging, and you may even float endlessly on one of the lazy rivers to relax and unwind from your park hopping adventures. Whichever park you choose, I just know that you are going to have a wonderful time!
Please do not hesitate to stop back by the Moms Panel if I can help answer any more of your questions before your trip. Have a magical vacation, Kevin!