I'm not sure I necessarily agree with the rental option; that's about $15,000 dollars (plus taxes, probably plus mileage) from e.g. CruiseAmerica. With a little care, it should not be too hard to come out better off with buying and selling a used motorhome or trailer.
It sounds to me like you aren't going to be staying at any one place for too many nights most of the time, but rather moving on every day or every few days, and having a lot of time on the road. A motorhome is in my opinion much more convenient for that kind of travel. Lunch can be had just by pulling off in a parking lot somewhere and walking a few steps to the kitchen. Likewise, a glass of cold water from the fridge is right at hand. It's entirely possible you would not need a towed vehicle, too, as you could fairly easily do your shopping etc. en route. I took a ten week trip to Alaska and back last year without a towed vehicle, and only once or twice did I really feel like it would have been particularly beneficial...but it is worth observing that others have different experiences and opinions there.
I may be all wrong, but I rather suspect you might not want to give up the RV after this trip.
