Time with me and rock. Children love rocks, always picking them up. One time one of my little girls was complaining about her backpack being too heavy. We sat down one evening and cleaned out her backpack. There was a lot of junk, yes but there was also about two pounds of gravel in the bottom of it; her "rock collection." We disposed of the gravel but I have never forgotten how all of my children just love rocks. Remember to spend time with your children doing the things that they love.