Hi pat
I was on the July trip
It was a mix from age 20 to 72 with one using cruches.
Great wall has some steep steps, but you do not have to walk the whole section, just do what you want to do (like some of even the younger ones did), sit and enjoy the view, use the local cafe for a tea etc..
JustYou use local guides which frees up the actual company rep who is always on the lookout for stragglers and you will find that people in your group support any who need to take things slower.
Chengde temples have some stairs to climb, but again you can take your time and your JustYou Rep will keep an eye out for you, as Daniel did for a couple of the slower in our group.
Tour is 'busy' in that we saw a lot of places, but have coach/train between them so plenty of time to relax.
If you want a taster, I have some videos on Youtube from the July tour (not all sites, just a few)
http://www.youtube.com/user/TrevTutor?feature=mhee#p/u
Trev