I agree with all others on here, to get an rv that you are able to operate by yourself. My husband also suffers from dementia as part of his Huntington's Disease. He is in the middle stages currently and his short term memory and cognitive thinking are the most effected, however he is still able to walk on his own. We have enjoyed our trailer for many years and thankfully I learned early on how to drive and work everything on the trailer so the transition to me being the sole driver/navigator was easier.
Also depending on how severe the dementia is, they can become lost very easily in a new campground setting. I do not leave my husband alone as if he wanders away from the trailer, he would not be able to find his way back. Thankfully, he still has enough sense to stay on the site unless I am with him.
We still enjoy camping very much and have our summer trips planned. I tend to pre-book campsites to avoid some of the stress of trying to find a campsite last minute. I say go for it as long as you can manage if it is not a financial burden. As someone else said life is short so go out and enjoy today