Hi Laurie! Thanks so much for stopping by and visiting with the Disney Parks Moms Panel!
Backpacks are permitted on the majority of the rides and attractions at Walt Disney World resort. Your backpack can be brought with you on the ride unless other instructions are provided. When I have a backpack, I usually put one strap of the backpack around my leg. This ensures that I don't forget it when I'm exiting the attractions.
Soarin' Around the World requires that you place your bag underneath the seat and
Avatar Flight of Passage has a storage section just behind the ride. So essentially your bag is kept with you the entire time that you are on the attractions.
Lockers are available to rent at each theme park.
A small locker is $10/day, large is $12/day, and jumbo is $15/day. A jumbo locker is only available at the Magic Kingdom and Epcot. Laurie, these prices are also subject to change without notice, so be sure to check the website or back here with us for the most up-to-date information.
Have a wonderful time at Walt Disney World. Please visit us again if you have more questions.
Happy planning,
Korliss