This is a classic game that can easily be adapted to reflect a Christmas party theme. The only preparation or modification you need to make for younger players is in the selection of simpler one word topics.
Inside every child is a ham waiting to come out. At a Christmas party select a few simple Christmas words and phrases for the children to act out. Have all the kids sit on the floor while one child stands in front. Tell the child what he or she is miming and let the other children guess. Once the correct answer is guessed a new actor is selected and play continues.
For older children the game can be more sophisticated. Have them break into teams and select 10-15 Christmas themed topics. The catch is they don't get to do the topics they create; they are for the other team. Screen the topics for difficulty, and assign a higher point value for the most difficult ones. This is a game of points!
Each team then selects the desired difficulty level and draws a topic. Then play is like above with one player trying to act out the clue for his or her team to guess. There is no stealing because the opposing teams created the clues. At the end of play, the team with the most points wins.
If you like the idea of being able to steal, then an impartial judge, this most often means mom or dad, can create the clues and keep them secret from the players. This also provides the opportunity to add a race element. Give all the teams the same clue, then they act simultaneously. The first team to guess correctly wins.