I guess I haven't gone to too many boardgame meetups, but D&D seems to have a pretty decent age spread to me; in fact, it tends to lean older than younger.

I have no comment on the dating aspect; I'm monogamously married, and have no particular opinion on the matter, though I will say that D&D leans so heavily male, I can count the number of women I've played with in the past six months on two hands without needing fingers. It's a problem in the hobby. :/