Xmas song suggestions

I was asked today to teach our primary kids a song to sing at our ward activity on the 12th of Dec. They're already learning Mary's Lullaby (with our Mia maids doing the descant) for the 20th. I think they want the kids to sing something else too. What song can they all learn in basically 2 weeks? Next week will be slim pickings since most of the kids will be out of town for Thanksgiving, and the following week we only have Sacrament because it's our annual nativity display for the community. Something simple like Silent Night would be fine, but does anyone have any fun suggestions to brighten it up a bit?