Hi Carol,
I did this trip in September 2022 and there is a review on the review page here if you have not seen it.
This is a brilliant tour.
As for walking you don't have anything to worry about. I did the entire trip wearing nothing more suited to walking than a pair of deck shoes!
At sites generally there are clear paths and walkways so there is no hiking as such and no need to go over uneven ground so you should have no trouble. At Mesa Verde we were actually parked quite close to the sights so there was not too much walking involved.
I did mention that one lady retired hurt - this was one of those freak accidents that could happen to anyone, anywhere and did not involve rough terrain.
Anything more specific then do feel free to ask
Ian