It's bizarre to me when hearing about these MMO addict parents. My memory as a kid is it was kids and teens playing games mainly, with some adults (who were usually also computer nerds). Adults would sometimes take interest, and may even play some with their kids, but it'll be for like ten minutes. They'd more ask about what the kids were doing later, listen, and that'd be about it.
Then there was always that one grandparent who never touched a video game before, and you and your friends would be stuck on this really hard level in an NES game, and he'd ask to try and would then proceed to fucking demolish that level, to the amazement and elation of all the kids.