Ideally, children are supposed to be a sign pointing to the health of the marriage. A strong union of love will always create life in a selfless way.
Likewise, God was perfectly happy in communion with himself, Father, Son and Holy Spirit. He had no need within him that caused a desire to create humans. Rather, his desire to create us was because he was so full of love and joy within himself, thus he made others out of love so they too could enjoy him. It was not an emptiness that made him make us, but the fullness within himself.
God’s creation is a testament to his love. So often with humans, however, the good we produce becomes a temptation to neglect those we love, mainly God.