I think Mona's takeoff point is a bit confused. Christmas Eve is not "the holiday," and most Christians would not think of their holidays as starting at sundown on the previous day, as Jews would. (Catholics sort of do, but only sort of. The big Christmas celebration is at midnight.)
Also in Germany the Christmas tree is decorated on Christmas eve while the kids are in Church, so they don't see the tree being decorated by the parents. It's the Christkindle (Christchild) who's decorating the tree and puts the presents under the tree. Then when everything is ready a little bell is rung and the candles are lit on the tree, when the kids are allowed the enter the room. I kept the tradition up when our children were smaller, but now they have their own traditions
About 15 years ago, on Christmas Eve, our family departed from the traditional American Jewish observance of the holiday (ordering Chinese takeout) and elected to find an open restaurant.