On this scooter is a child who's trying to show that his lineage is humble. All of the other children are going around in fancy cars or helicopters, but this one child wants to be a humble child of the people, so he scoots on a plebeian scooter.
This humble child is your son (そん). You don't want any child of yours flaunting his wealth and good standing in the faces of other people. You've taught them to be humble.