C's Mom&Dad,
We rented cars during our three RV rentals. It was difficult at times as not all locations offer rentals like in Guerneville, CA. In our experience we found that sometimes the rental agent cannot get to you right away. We tried to rent in Napa Valley, CA., and we had to wait a couple of hours. In Lake Tahoe, CA, they only had a mini van which was much bigger than we wanted. Sometimes you can't get choosy.
We could not get a rental car from a 'big' company in Sedona, AZ, only from a secondary company that rented used cars. The only way to rent from the large rental companies were to fly into the airport.
I just wouldn't want to be tied to the schedule of a rental company. I would buy a small light-weight tow vehicle (Honda Fit or something similar).
Unless you plan your stops really well, unhooking to run to the store is a headache. Not a big enough reason to rent but you might need to make a quick visit to a store.
MM.