Candy Cane Holiday Wreath- This is probably the easiest idea to have your kids do. The styrofoam ring can be found in the craft section/store, yarn and any decorations you like to add. Wrap the yarn and tie off. Use yarn to tie the decorations on also. No gluing necessary. Instead of yarn you could use strips of wrapping paper and tape it around the ring.
Possibly the simplest centerpiece ever. Small favors can be used on a mirror or charger. Sprinkle with jolly ranchers, mints, Hershey's kisses, or your favorite candy. You can even add smal kit kat bars with personalized wrappers from www.customfavors.com.