My favorite holiday cookie recipes are from Bon Appetit magazine. If you are making these with young children, I would recommend doing the baking project over two days. Make the dough one day, and bake and decorate the next.
When decorating cookies with young children I like to portion the frosting and sprinkles into little cups so it is easier for them to use the materials. This also helps with clean-up at the end.
Here is the link: