A couple of years ago (the last DC I attended) my mother was in a wheelchair due to a leg injury. We got there after the sessions had started and didn't know where the wheelchair seating was (it used to be in a certain room, but they cancelled using that room that year). I had to ask several attendants before we found one that told us where some seating was. There was a spot for her wheelchair and a seat for me. The attendant told us we could only sit there for the morning because that spot was "saved" for the afternoon. This came from an attendant!!!!
I have to say I was disgusted with the whole arrangement for people with special needs. There wasn't even enough reserved parking, I had to drop my mom off and go and park in BF Idaho. If she was by herself in a chair, I don't think she'd have been able to manage it.