Follow the link in my signature or look near the top of this thread for the disABILITIES FAQs thread.
Posts 18 -21 have access information and do indicate which have wheelchair accessible ride cars.
Post 34 on page 2 of that thread has information about where the accessible seating for shows is located.
If a show has Fastpass, guests using Fastpass will enter before guests with mobility devices who are using the Standby line. The front row or other choice spots may already be taken by the time Standby guests are allowed in.