This is an unusual request and (hopefully) there should be a good reason. Note that in many of the theaters they have seating in the last row with often large spaces between some of the seats for parking EVCs and wheelchairs.
When you go to the first park you are best off going inside to Guest Relations. They will give you a GAC thta is good for the four parks for your entire stay and the person with the disability plus up to five additional people.