Hi, Susanne! You are going to be amazed at how accessible and accommodating WDW is for family members in need of special assistance. My mother has traveled all over the world (in her wheelchair and/or with her walker), and my parents keep returning because WDW makes it so much easier to get around and enjoy experiences with the entire family.
Yet, some parks and attractions were designed and built before the Americans with Disabilities Act, and although WDW has made alterations for those guests with mobility issues, some attractions and locations aren't quite as "friendly" as others.
For a complete listing of attractions, please read over
the WDW Guests with Disabilities Guide. I've linked you up specifically with the page on mobility issues, but there are also guides for those with other limitations as well. You can learn when your daughter will be able to exit her chair or when she can just roll right up to the entrance and board just like everyone else. As a general rule, the newer the park or attraction is, the better the accessibility is. Therefore, ask a Cast Member whether or not you're able to board in the general que or if there is an alternative entrance.
One of the first things you'll want to do when you arrive is to obtain a Guest Assistance Card which you can receive at Guest Relations at any park or at Downtown Disney. This will easily identify your traveling party and allow for you to use alternative entrances for attractions and viewing areas for entertainment. There are several guidebooks that address the specific needs of WDW guests with disabilities, and there is a site and dedicated guidebook as well at www.diz-abled.com. You can read about what to expect for your maximum efficiency and enjoyment.
Thanks for visiting the Moms Panel and come back if you have more questions. Have a wonderful day and a most magical vacation!