Choosing games for the room you have got
For a big group, anything over fifteen people, pick games that run in teams and keep everyone busy on every turn. The hat game, Christmas Family Fortunes, name that intro and steal the present all hold thirty people. Charades works if you run two rooms at once. Avoid anything where people wait in a circle for their go, because by the time it comes back round half of them have gone to the kitchen.
For a work Christmas party, the question to ask of every game is whether the newest person in the team would be comfortable playing it with their manager watching. Team games with general answers pass easily: name that intro, a blind tasting, the hat game with celebrity names. Superlatives work if the awards are gentle. Never have I ever, and anything built around drinking, does not belong at work however well the team gets on.
For a family, mix one physical game, one guessing game and one game with a prize, and play them in that order: the chocolate game while there is energy, Family Fortunes when everyone has sat down, steal the present to finish. Pair the children with adults on teams rather than making them compete against grown ups, and give the smallest ones a job, like working the music for pass the parcel, if they are too little to play.
On prizes, cheap is funnier than good. A chocolate orange, a paper crown with "champion" written on it, a trophy from a charity shop that has to be returned next year. A running trophy that passes from winner to winner every Christmas turns the whole thing into a family institution within two years.