One fun craft would be to make candy canes out of pipe cleaners for the kids to hang on the Christmas tree. And, depending on the school, you might even be able to tell the story behind the candy cane while they are making them. It doesn't take that long to do, but it's one idea to fill the time.
They could also make a card for someone in their family or a friend. Maybe have some fun colored markers and stamps for them to pick from. I have never bought stamps, so I'm not sure on the cost of them though.
If someone is bringing snacks, they could bring in gingerbread cookies and get some tubes of icing from the store for the kids to decorate their cookies with.
You can also spend some time singing carols. :)
Again, these things may not take that long to do, but they're just what came to mind right away.
Hope that is helpful. Oh, and you can find the directions for making the candy cane ornaments online pretty easily, I thing. I would just Google 'candy cane pipe cleaners' and see what you get. Or even 'candy cane crafts' as I know that one will bring some good results.
Good luck with the party. :)
God bless,
A.
P.S. The story behind the candy cane is really easy to find online as well.