I've taken two Trafalger (and some other) tours, and the age distribution is older, 50s to 70s, as I am. Primarily I think because we have more time. Usually there are some people in their 20s and 30s, and they are welcome as well. It ends up like a family with the young folks and the old folks.
That means the pace of the tour is fairly relaxed, even tho some of us wrinklies walked the kids into the ground.