Pass the Parcel, musical chairs, dead lions, have a dance-off.
Supply loads of those glowsticks that you snap to activate, they can be made into hats, necklaces, bracelets etc.
Have a big bolt of paper - like cheap roll of wallpaper because it-s tough. Kids lie on it like a gingerbread man, you draw their outline and they colour it in, it can be taken home to finish and adorn their door.
Christmas/ themed pinata before they leave, don-t buy one, just use any kind of box, make it easy enough to bash.
For food, i-d have a little plate prepared for each with food already on it\in a cute paper bag, ready at the table. Buffet style would be chaos!
My parents always threw a Christmas party for me and my sibling on Christmas eve, admittedly there were only two of us! Fantastic memories.