Hire a bus/van/stretch limo to take you for a drive through the Christmas lights in a town not far from where you live. Make the driver honk when you see one you like.
Rent a local venue and host a little party for friends, family, neighbors, etc. Play games like pairing up and finding out 3 things you have in common with your partner.
Stage an event for the residents at a local retirement home with snacks and entertainment and maybe a small gift for each from the Dollar Tree, etc. - you can sing and it doesn't matter if you're bad because many will not hear very well anyway). Ask each resident to share a favorite (Christmas) memory. (I've done this, it's very moving...bring Kleenex).
Have a jigsaw puzzle tournament. Get two or three puzzles that are exactly alike, choose up teams of 6 or 4), set a timer to go off to start you all and see who can put their puzzle together first. Or, set the timer and whoever has the most pieces in at the end of an hour wins.
Get some supplies like paper, crayons, markers, etc and see who can make the best hand-made Christmas card, then each player give their card to another person in the group. Or, mail them to a VA hospital (for example).
Get a professional family portrait done. Schedule several poses with different clothes. If you can't afford a photographer, do it yourselves with your own cameras.
Make a video of you all saying what you love about each family member. Real keepsake. (bring Kleenex for when you watch).
Have a bake-off and see who can turn out the best cake (or cookies or whatever). Would probably need a large kitchen for this.
Play "I accuse" where you pick a person to be "it" and then the others write accusations on little slips of paper. Stuff like "I accuse Grandma of smoking a pipe when no one is looking." She will deny it and you all can say, "See? When no one is looking!!!" etc etc. One person reads the "accusations" and the person who is "It" tries to guess who said them. Person with most correct guesses is the winner. Of course, there has to be a prize...don't play this if you have sarcastic people in your family, though. Could get ugly quickly.
Most importantly, have fun and enjoy each other while you are still all around. Time can go more quickly than we know.