Hi, Amy, I found that at age 4, my kids still needed a stroller at Disney. There is just so much walking! You can either bring a second stroller, a double stroller, or just take the one you have planned, and if you find you need a second one, you can rent one. For more information on stroller rental, click
HERE.
While you are on attractions, there will be "parking lots" where you can leave your stroller. Strollers do get moved around, and it may not be where you left it. To help find yours, you might want to tie a bright ribbon around it or have some marking so you can find it easily in the swarm of strollers!
I always like to have my backpack so I can carry it easily when we go into restaurants or on attractions. Also, my husband can take turns carrying it!
I hope your boys have a great time in Disney World!