Nat Geo/G Adventures to Peru - Suitable for a 50 y/o?

Hi!

I've seriously been considering booking with National Geographic/G Adventures and going to Peru. My father has recently expressed that he might be interested in going with me on the trip.

I was just wondering whether anyone has experience with this tour, the physical requirements, and the general age demographic?

I know most G Adventure tours are usually made up of solo travelers, with the occasional pair of friends, siblings, or a couple in the mix; it isn't an 18-to-30-something tour (or, it's not advertised as such) so there's nothing saying that he will be the oldest one in the group but I am aware that there is a distinct possibility that happens. He gets along with everyone so I'm not worried about him socially, but I would like to give him a bit of a 'heads up' on what this tour is actually like though it's a little difficult when I myself haven't gone so I have no idea lol

Any answers are appreciated! Thanks!