Hi Megan, welcome to the Disney Parks Moms Panel.
I am just like you, when I am at the WDW I can’t think of wasting any minute! I am always doing something.
It is perfectly fine to go to a Water Park and a Theme Park on the same day, especially if you have a
Park Hopper ticket. I did it a couple of times and it worked pretty well for my family. What I do, is to leave the Water Park around 04:00 p.m., and head to a Theme Park we have already been. We can repeat some rides we like, have a dinner at one of our favorite restaurants or watch amazing fireworks.
You could also go to
Downtown Disney Area instead of a Theme Park, depending on how tired you all will be. That is a perfect place for spending some fun time with your family. Nice stores, great restaurants, a very good place to walk around and relax.
Come back again if you have more questions.
Have a magical vacation!
Gina V.