I second the recommendation above about finding non-walking options. A few years ago we went to San Francisco (I live in the midwest/USA) and was excited but knew from visiting there before that it would involve hills and walking. We did the Red Bus tour and could get on and off at sites and I managed my walking. I could also hang at a park with a book while my family walked about more and met back up with me to get on the bus.
I’d really like to get to places in Europe and the boat tours interest me where I could stay on the boat and family could bike to the next port and meet up with me. Often there are options to still enjoy with others and let us each do what we can do-
I’ve also seen this forum put to good use asking people in those regions for advice on support and services. You may be able to find forum members in the area that would have good advice of what to do in that area to enjoy it fully without vacation dread-