When my children were small, we read a book together that started a tradition which carries on almost twenty years later. If you have never read "A Chair for My Mother," it might make a great gift for a grandchild. The story is told by a young girl who worries about her mom coming home after work each day, tired and worn. They have very little- certainly no comfortable spot for her mother to rest her tired feet.
They start saving all of the change the mother and daughter get each day, putting it in a big jar. When the jar is full, they bring it to the furniture store, and buy one cozy easy chair where they cuddle contentedly!
My children and I started our own jar. When it was full, the change was counted and put in wrappers. Then we would decide what to use it for. Over the years, we have gone out to lunch, bought gifts for those in need, purchased a game we all liked and given it the youngest (and poorest!) family driver the proceeds for gas money.
Now they are all grown and on their own. I still fill the jar, and use it as my surprise! money. I may spend it on myself, treat a friend to lunch or dinner- whatever my whim decides!