Are you looking for something that takes place during school hours or outside of school hours?
2 years ago we had performing company come in a put on the Charles Dickens play "A Christmas Carol" as an assembly. The kids enjoyed it and after the show they let the kids aske questions and and talked to them about acting & about how you put on a play.
A non school hour event we hold every December on a Saturday morning is called "The Holiday Workshop". They charge the kids a minimal amount to come ($2 to cover the cost of the crafts). Our school is K-3. K -1 come first for 1 1/2 hours and then grades 2 & 3 come for the next 1 1/2 hours. The lady in charge buys most of the crafts from Oriental Trading and she gets a group of volunteers to individually bag them for the kids. They play holiday music and serve cookies & juice. The kids enjoy it.
Make a Gift is a fun activity for that age group. Our YMCA does one every year and my kids love going to it to make gifts for everyone. A Holiday shop for the children to shop at. Do a Winter Fest with activities, carolers and Hot Chocolate.