Well, I'm going to preface with the fact I know nothing about coach tours...never been on one.
I guess I liken them to cruises. Been on one of those.
There are themed coach tours that would bring all ranges of people. I would imagine if there's one to Glasonbury for the concert, that you might find a real interesting assortment of people.
I think years ago many more families were taking coach trips, but with more families having cars these days, I venture more pensioners are filling the seats. And...more coaches are leaning toward the pensioner in their advertising and service for that reason.
I'd say your parents would have a really good time on a coach trip.
Then it occurs to me that you might be referring to just a straight National Express ride? Or a bus? Both those are just big vehicle rides to places. I've been on those. A mixture of people, but the drivers are always very accommodating with the seniors.