Fullcurl...
Oddly enough there are lots of folks down here that are not disabled and still shoot elk from on or very near the road.
You shouldn't have too much trouble getting your dad onto a cow if he can manage a short walk to get off the road and shoot.
I am sure there are lots of folks here who can get you guys pointed in the right direction as far as likely places to hunt.
Good luck and good on your dad for not letting his troubles keep him out of the field.