So I have this great idea, what you think
Start here, and see what they could suggest. I can't think of a better way to get started and make a difference in someones life.
http://www.woundedwarriorproject.org/
Kudos to you.
You fought the good fight and won. You could / will make a difference in others lives.
There are also other organizations that do exactly what your describing in regards to building cars with and for wounded vets as therapy for them.
I just can't remember what they are at the moment. Search a little and you will probably find some in your area.