Our RV has been a lifesaver for travel with three special needs kids (and at times up to 5), physical and mental disabilities. I agree that there are rentals available to be set up on site that would be suitable while you are there, but that option depends a lot on how much stuff you have to transport, whether your kids need special seating, the age/sizes of your children, whether the equipment needs to run enroute, and what your other means of transportation might be.
We have two on feeding tubes and pulse-ox monitors, one on oxygen, two with little trunk control requiring special seating, one who can sit in a regular seat and eat anything that gets close to him, and one who can eat some 1st and 2nd baby foods. All these "problems" are rolled up in three children and a lot of equipment. It would be next to impossible for us to travel any time or distance without our MH. We put the special seating on opposite sides of the MH, one on the sofa and one in the recliner. The third rides shotgun and "studies" the map a lot. DW finds a seat wherever she can...sofa, dinette, bed.

We also tow a cargo trailer with the wheelchairs, GC, extra formula, baby food, oxygen tanks, Christmas decoration in season, etc.
So it just depends on your specific needs for travel, and what your budget allows, as to what a good solution would be. My observations have been that most reputable rental companies rent Class C's. Private rentals are rare and require special precautions for liability, insurance coverage, quality of the product, etc.
Best of luck on settling on the choice that will serve you best. Please be sure to post continuing episodes in your search and decision process.
