Hi there, Ty, and welcome to planDisney! Thanks for stopping by with your question about whether sling bags are allowed on Walt Disney World attractions. Let's get right to it!
You are permitted to bring your bag with you on most rides. Some rides like
Soarin' Around the World (soon to be
Soarin' Across America) have a basket for you to place your items. For this ride specifically, if your bag won't fit, Cast Members will ask that you leave it on the ground in front of you, and they will move it to the side for you to retrieve as you exit.
TRON Lightcycle / Run has lockers within the queue for you to stow items in. Just make sure you remember the locker number so you can collect your belongings as you leave the attraction. You'll put your bag at your feet for most other rides. If you have any questions, ask one of the friendly Cast Members at that attraction. They'll be happy to let you know what's best for that particular experience.
I'd also like for you to know that
locker rentals are available at each Disney Theme Park if you don't want to carry your bag around all day. I'm a big fan of renting a locker because I find my park days are much more enjoyable the less I'm carrying. Plus, renting a locker gives me a place to store purchases once I hit up the merchandise shops.
Ty, I hope this has been helpful, and please stop by again with any other planning questions you have.
Let your dreams guide you!
Melanie