Is the John Quincy Adams tour reasonable for a 10 year old and her semi-disabled Nana?

There is a fair amount of walking. I would wait until summer for dry surfaces.

Depends on the disability and how it affects her walking up and down stairs. There was a man on crutches in my tour group, and they had him and his wife drive their own car to the locations instead of riding the tour bus. They missed out on some of the narrative because it took them longer to get to the different places (the tour is on a strict time schedule as they are run throughout the day, so they don't have too much time to wait for people who lag behind), but they were very helpful and accommodating to him so I don't think he missed out on much of the experience.

If they enjoying reading it's ok

Umm maybe not so much for. Semi disabled. But you might want to call and ask if it's ok enough for a semi disabled. As far as the 10 year old it's fine