God provides for us what we cannot provide for ourselves, what is essential if we are to survive. There are other images that present this superiority and providence, but no other image combines them so well with the primary attribute of God in relation to us, which is love. God loves us like a father loves his son, like a mother loves her daughter. Of course, whenever you say something about who God is, you are also saying something about who you are. And when 1 John celebrates that we are the children of God, it is telling us how we ought to think of ourselves.
Children are cute, precocious, wise beyond their years.
They are innocent, gentle, dependent, and obedient. They can be fragile, ignorant, and filled with unfounded fear. More than anything else, children are growing. They are bundles of potential, promises waiting to be fulfilled. Parents delight in wondering what their children might grow up to be.