I am sorry that you and your husband are facing this diagnosis. My dad was diagnosed with dementia(not severe) and had some other health issues, but enjoyed travelling. We have a motorhome and it was great having his own bed, our own bathroom, and not hauling suitcases in and out of motels. He would often lie on the sofa while we drove down the highway. We took him on numerous trips around our state of Texas, visiting relatives, and even took long road trip up north too. We paced ourselves so not to wear him or Mom out, would camp for several days, or just overnight. We traveled several years until his health worsened. I am so thankful that I could do this for him. I choose a motorhome because I did not have experience in towing a vehicle. If we stayed somewhere for several days and needed transportation, we rented car.
My suggestion:
As some of the other posts said, check out many different style RVs, find what you are comfortable with. I rented a small Class B+ RV to get the feel of driving it before I purchased our Class C 30ft.
If you and your husband enjoy traveling, go for it while he is still able to travel. Make the memories while you can.