Yes, at large family events like Thanksgiving my mother has been known to not just bring empty containers for leftovers, but to bring enough for everyone at the meal to take a couple! She does, however, not bring them out until the question comes up naturally.

Yes, we do this, too. (For Christmas, b/c we don't have Thanksgiving.) Containers in a bag that gets left with our purses, and when the leftovers are offered (they're always offered; we have oodles of food because everyone brings a plate like their dish is the Only Thing That Is Going To Be On Offer For Lunch) then we have our own containers and no need for extra plastic.