Seeking advice: rehab exercises for the disabled

My father’s recovering from a nasty systemic infection that left him unable to stand; I’m looking for advice on how disabled folks can use qigong &c to help with their rehab. Details are below, but the main questions:

1. When someone’s disabled and can’t do qigong exercises the way they were designed, what’s the best approach to take?

2. Are there any sets designed specifically for wheelchair-bound (or bed-bound) people?

3. What are good ways to find handicapped-friendly instructors?

Some dad-specific details: he was diagnosed with MS at age 16 and has been managing things with daily exercises ever since — he’s 73 now, was walking with a slight limp until he was 28, with a cane until his mid-30s, and with canadian crutches until he was 71. At that point a broken leg that’d been set slightly crooked 30 years ago came back to haunt him: its loose knee joint started to buckle sometimes when he weighted it, so he started using a walker for safety. In April last year he developed a UTI and went to the hospital to have it treated, another UTi developed in June, with a slightly longer hospital/rehab stay. Finally, he developed a serious systemic infection just after Thanksgiving last year; they broke out the heavy duty antibiotics to treat it, which kept him from moving much, and he was in hospital/rehab until July of this year. He’s at home now, with visiting nurses/physical therapists, and while he’s working on standing he’s still wheelchair bound, because the once-buckling leg now will go into a big spasm whenever he tenses up — obviously not a healthy thing for him to stand on. He is well used to handling disability, so would regularly perform any exercises or sets he could learn.

PS. If anyone can recommend specific handicapped-friendly instructors in the Boston area, I’d love to hear ’em!