Hi there, Mindy!
While your plan is absolutely awesome, you have already made a realistic assumption: that you will be shorting yourselves if you attempt both in one day.
The water parks are actually "labor intensive". There's lots of walking; not only are the parks themselves sprawling and spacious, but there's the uphill element, too, in order to access the slides. While you might be able to "complete" one water park by late afternoon, say, the fun of the day might very well have worn out your traveling party to the point that a good dinner and an early night sound like the best plan.
And you definitely don't want to exhaust yourselves! Certainly hitting up either
Typhoon Lagoon or
Blizzard Beach is a must-do, but not at the expense of the next day's activities.
Have a wonderful - and realistic! ;) - trip!
See you later, celebrator,
-Deborah B.