I thought this was a cute idea, it not only teaches kids to re-use and be mindful of consumption, but also about helping others. Once done you can hang the hands on a string and try to do one each day, or each week or month if you want the giving to go beyond Christmas.
I truly believe if you teach your kids to enjoy the great feeling achieved by helping others, they will want to continue that through their lives.
"Cut out your child's handprint from card fronts of Christmas cards. On the back of each hand write a kind act your family can do for others."
~Helen Coronado, author of Eco-Friendly Families. Source: Woman's Day Magazine vol. 72 Issue 3