If your children are young and you wonder what all they can help with, I found a really nice guideline in an article here on FamilyFun. It will give you some ideas of what each age may be able to do.
1 C. margarine
1 1/2 C Sugar
2 3/4 C. flour
2 tsp. cream of tartar
1 tsp. baking soda
Cream sugar, margarine and eggs thoroughly. Add dry ingredients and mix well. Roll into balls about the size of a walnut and roll in a mixture of 2 T. sugar and 2 tsp. cinnamon. Place on ungreased cookie sheet and bake at 400 degrees for 8-10 minutes. Remove to cooling rack immediately. Should make about 3 1/2 - 4 dozen delicious cookies!
Here are the proud bakers with their yummy results!