Jay, first of all, props to you on your endeavor. I am a hard arse most of the time, but have a soft spot for the disabled.
I dont have anything to add as far as ideas to help him fish, but I have a feeling that he may not care if he participates in catching the fish at all. Just spending time out on a lake with you may be all the excitement he is looking for. If you can make the fishing rod/reel happen for him, all the better. Dont let time go by just because he isnt able to physically participate.
As I said, the mere act of being there with you will likely be one of the best experiences of his life.
Nice work.