Hi Amanda ~
I have a teenager with Cerebral Palsy and we are very grateful for the
services for Guests with mobility disabilities at the Walt Disney World Resort. On the link I've provided, there is a list showing which attractions will allow Guests to remain in a wheelchair and which ones require Guests to be mobile to enjoy.
For attractions that require Guests to transfer, some of the attractions offer special ride vehicles that open up a little wider to give Guests in wheelchairs more room to transfer. Dumbo The Flying Elephant, the Seven Dwarfs Mine Train, and Expedition Everest immediately come to mind. You just need to alert the Cast Members in the boarding area that your sister would like to sit in those vehicles.
For the Mad Tea Party, they can open one of the tea cups up a little wider and give her a stool to help her slide into the vehicle.
Avatar Flight of Passage has a special wheelchair that will help her transfer to the ride vehicle. This one is great and makes transfers really easy.
The Na'vi River Journey has a device that Guests can use to get into the ride vehicle. It looks like three steps which goes over the side of the boat onto the seat. She may need someone in your party to help her get her legs over.
Frozen Ever After has a device that looks like a wide step that hooks on the side that she can use to lower herself down.
Mission: SPACE has a transfer device that looks like a little bench that Guests can use to get closer to the ride vehicle and slide in.
Keep in mind that Cast Members are not allowed to physically help Guests with transfers so if she needs assistance, someone in your party will need to assist her. She should always take her time and never feel rushed.
I'm limited in space but please feel free to visit again. Wishing you minnie magical memories :-) Allison V.