But, the trick at Haunted Mansion is that:
1) First you have to walk into the stretching room from where your ECV/wheelchair is parked.
2) Then, you have to stand for the stretching room show.
3) Then, you join a slowly moving throng of people walking in almost dark to the boarding area. The line gets gradually narrower to deliver a single file line of guests to the boarding area.
4) The moving walkway can't be slowed or stopped there.
5) After the ride, you will need to walk back to your wheelchair or ECV.
I think I can do all of that if I don't have to add an hour of winding in and out of the queue as well. If they'll just let me sit in the scooter until it's my turn to enter the stretching room, I'll be ok.
After the ride, I'll be sending one of my sons to get the scooter for me. I don't know how it is in the MK, but in DL, the exit is quite a walk from the entrance.