It seems to be impossible to rent a wheelchair-accessible minivan in either Jackson, WY or Boise, ID. I’ve done internet searches and made many phone calls, and so did the concierge at our hotel in Teton Village, The Hotel Terra. You can pay Bill Phinney (see Raves) about $1000 to drive a van to your destination in either Boise, ID, or Jackson, WY, or you can pick it up from him at the very-manageable airport in Salt Lake City and drive it where you want to go. Check out the rental site: www.wheelchairgetaways.com/franchise/utah_saltlakecity/. We rented a side-entry (electric in-floor ramp) Dodge Caravan; it was clean and in good shape.
We opted to stay overnight in Salt Lake City and drive: first to Teton Village in Wyoming (about 5.5 hours) for 9 nights, then from Teton Village to Boise, ID (6 hours if you take the 40-minute detour, as we did, to the Idaho Potato Museum in Blackfoot, ID) for 4 nights, and then from Boise back to Salt Lake City (another 5.5 hours). Bill makes the exchange easy: the Salt Lake City airport is relatively small, and he meets you at baggage claim on your way in and curbside at a handicapped-parking space on the way out.