Another older person here, writing what I think some of the younger ones I met might say if they were looking in on the forum...
On the Norte, August 2013, somewhere between Aviles and Mondoñedo some people who walked about the same speed started to walk together more, pick a set of bunks together, have breakfast together, cook communal meals and look out for each other. By the time we got to Sobrado we were six - two german girls aged 17 and 18, and trainee policeman in his early 20s also german, two women in their 30s (english and spanish) and me.
When we reached Santiago the teenagers headed for Finisterre and I did the Ingles. We met by chance five days later in Santiago (as you do). I was really taken by how they had changed since first meeting them - now with so much more self-assurance, able to appraise other adults and the world eye-to-eye. I think that was partly their sense of achievement, but also from being part of a group of all ages where they were equals, not typecast as kids or teenagers, but as people with views and contributions that were equally valued in our joint enterprise. I think the dynamic of a group of more than four or five young people travelling together would typically work against this kind of dividend.
Barbara, I don't know whether it's feasible to try and orchestrate this kind of mix and experience, but it's worth considering!
rgds, tom