A few months ago I spent a day at respite home for disabled people and did mini treatments on several people with different needs. Most were in wheelchairs and some of the clients were able to be hoisted onto my couch using the electric hoist (quite time consuming, and needing two carers so I needed to add probably 20 minutes either side of the massage).
Some of my clients, however, were too nervous to be treated on the couch so I was able to work on them in their wheelchairs. One lady's wheelchair had a fold down back, so I was able to work down to the lower thoracic area. On others, I was able to get the client to lean forward slightly, so I could work down as low as possible. Also worked the head, arms and hands.
When working with disabled people, the most important thing is to be adaptable, to know what the person's disability is and how it affects them (do they have pain, discomfort, weakness or no feeling at all in certain areas) and just work with what you've got. Some people, for instance, may only want a half hour hand massage, so it's important to be able to have lots of different techniques to work an area.
I would also add that the work is extremely tiring, you may find you have to get into some strange positions to treat, so watch your back. However, it is so very rewarding, so enjoy.
Lesley