It is certainly possible for a paraplegic to paddle, and well. I was soundly beaten in the Sea Trek race around Alcatraz (not the easiest of courses) several years ago by Mark ?, the man who returned to climbing (El Capitan in Yosemite, among other challenges) after losing the use of his legs.

I suggest that you get in touch with Environmental Traveling Companions here in California for expert information. I know that there is a book on the subject as well, so a little searching should turn that up for you.