Here in Europe most of the Casino chip collectors are mid age, I guess I am the oldest, and a few young guys are starting to be interested on it.
I think the problem is not the age, problem is how to enlarge the collection without spending a lot of money.
Now almost all casinos have at least a couple or three Holdem Texas Tournements around the year, young people likes it and travels from one side to the other just to play it.
Talking with them is a good solution, tell them to keep a couple of chips from each casino as souvenir, as far as they get twenty or thirty they start to get interested and ask how to get more.
It's not easy neither cheap to collect Casino chips, but I guess it's something like a drug, you start once and after you can't stop.