I'd have done the same bozz.

Like no joke my wife tries to get me to help my father-in-law all the time and I tell her no, let him keep his pride. My father in law is getting old, but the women sure do fuss over him in our family, and I always feel bad for him when sometimes I'm marched over to help him with what he seems like jobs he has handled easily.

Anyway, good for you. Leave the young couple alone. If it were me I'd have waited until they finished, took them over a beer and started up a discussion and during it, casually mention how long I've been doing it and the tools I acquired.

Then if they wanted help they'd ask :)