Hi there, Brandi!
Welcome back to the Disney Parks Moms Panel. I'm so glad you decided to stop in with your question!
If you're planning to park hop between Epcot and Disney's Hollywood Studios, you can definitely park at Hollywood Studios and use the
water taxi to get to Epcot. When you're headed back for
Fantasmic! later in the evening, just allow yourself about 30 minutes to get there by boat since you'll be making a few stops along the way. You're very smart to leave your car at Hollywood Studios so that you can get back to it easily after the show.
I sure hope you have a great day visiting these two fabulous parks and you find the water transportation to be a nice, relaxing trip. If you have any other questions, just let us know.
Wishing you a magical day!
~Carrie