Hi James,
Staying hydrated is super important at the Walt Disney World parks and resorts, so a hydration backpack is a great idea and perfectly okay. Guests are welcome to bring backpacks of any sort that are no bigger than 24 inches long by 15 inches wide by 18 inches high.
You can bring nonalcoholic drinks and snacks with you into the parks in your backpack or tote. You can find the list of any
restricted personal items on the Disney website.
All Walt Disney World rides can accommodate your belongings. On most rides, you can put your bag on the floor of your ride vehicle or in a pouch in front of you. On the new
Avatar Passage of Flight, there are storage bins behind you for your gear.
The only ride I know of with lockers is
Kali River Rapids at Animal Kingdom. Because guests can get soaked, free lockers are provided at the ride entrance to keep your things safe and dry.
Another note about hydration: You can get a free cup of ice water at any counter service location. There also are water fountains throughout the parks and a few water bottle filling stations.
I hope that helps, James. Thanks for visiting the Disney Parks Moms Panel. Please let us know if you have any more questions as you plan your
Walt Disney World vacation. Enjoy!
Wilma