Set out the bling. Small bowls, cupcake liners and paper cups work well for holding decorations. If you like, put out a selection of other decorating tools, such as toothpicks, new paint brushes (kid-size), and plastic knives so those who want to spread things around can do so easily.
Provide paper plates for guests to take their masterpieces home. Guests can decorate their cookies right on the plates and write their names on the rim. The plates slip easily into gallon-sized zip-top bags, keeping the car trip home neat and clean.
Serve something besides sugar. Have something simple to eat so everyone doesn't fill up on cookies. I usually make a hearty soup or stew and serve it with some good bread. Hot chocolate and warm apple cider are great beverages for the party (and perhaps a little mulled wine for the adults). For dessert -- cookies, of course!