Here is my sugar cookie recipe-- I don't remember where we got it from, but it works fine so if you don't have one... Here you go.
For St. Patrick's day we did green cookies with sprinkles. Thing-one piled the frosting about 2 inches high and had almost the same amount of sprinkles before she declared her cookie ready to be eaten. Thing-two was in a hurry to take bites out of all the cookies she could. I showed her how to spread the frosting and helped her to try it out along with shaking on some sprinkles. It was fun for all of us.
Now go have some fun with your kids.