Jodi:
Our family has made many trips where we only visited Disney's water parks. They are an excellent value.
I usually recommend that you visit them on a weekday rather than a weekend so that you can avoid traffic from local residents but even this is being managed better now that Disney has blackout dates for those who purchase the Florida Resident tickets. Speaking of blackout dates, I noticed you are from Florida, so check your tickets for blackout dates if you have discounted tickets.
Just like the theme parks, the water parks are no different when it comes to crowd control: summers have higher attendance so arrive before park opening to grab a chair and do as many of the slides before you have a wait. Personally, I prefer the pre-school area at
Blizzard Beach to that of Typhoon Lagoon because of the seating area and higher sides to the slides, not to mention better visibility of my child as he goes down the slide. Its
Ski Patrol Camp provides just enough thrills for your 9-year-old and adding to the fact that I feel the wave pool at Typhoon Lagoon may not be appropriate for all children, especially if they are not strong swimmers, my recommendation is to choose Blizzard Beach.
Wishing y'all a magical vacation!
Whitney