A really good game to play at Christmas is "statues."
It works because the adults can play and you can always get one of the kids to beg them. Just make sure that you get the kid to beg before they are wearing half their dinner on their face and while the crinolines are still crisp. For some reason wilted crinolines and gravy do not equal cuteness.
You can do the "pretend we are all little mice and be as quiet as quiet as can be" but chances are their parents have already played that one to death on the ride over Christmas morning.
Have everyone strike a pose and hold it. You can also call this game "playing Madonna" which might win over the hearts of some of the more trendier peeps. They are not to move or speak. Then you tell them there is a huge prize for the winner out in the garage and you leave them to it.
The prize is room to move and not be a statue ... but don't give that away until the end. I sometimes LET the kids win and declare it a 32 way tie and put all the kids out in the garage ...that works too.
Oh just make sure to check on Grandma every now and then ... sometimes it may look like they are playing Statue and they are really dead.
SKIN: .::WoWSkins::. Britney tone 1
EYES: IKON 'Sunrise' Eyes - Eggplant Pale v2
EARRINGS & BRACELET: Ear Candy ~ Black Hey Babycakes
NAILS: [Bamboo] Nails - Highlighted
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POSES: Cranky House