Hi Jaynee!
Your family will find
Walt Disney World is quite disability friendly. All transportation is accessible, most queues accommodate wheelchairs, and walkways are wide. EVCs and wheelchairs are available for
rent at the parks, but they may not leave the gates. No wheelchairs or EVCs are available at the
Walt Disney World Resort hotels, so
Disney's All-Star Movies Resort will not have a wheelchair on site for your brother to borrow.
If your brother needs an EVC to transfer to his room, he can start his rental a day earlier. Disney's preferred provider, ScooterBug, can leave an EVC at Disney's All-Star Movies Resort without you being present. You are, of course, welcome to use any outside vendor you wish, but a family member will need to be present for delivery. Since your sibling needs a scooter to reach his room, having it waiting for you at the resort might be easier.
Wishing your family a wonderful visit to Mickey!
Elisabeth