George MacDonald was quoted as saying something to the effect of: "did it ever occur to you that God created you for one purpose: simply to love you". All the stuff that we do would then flow from experiencing that reality. This would suggest a view of us as God's children (indeed, in Gen 1, the point is arguably that in the end, God reproduces after his kind [as much as is possible]). I don't have kids, so I don't no, but it seems like that is ideally why people have children--to love them.
The Westminster Catechism is related: "What is the chief end [purpose] of Man? The chief end of Man is to glorify God and to enjoy him forever." It is less satisfying, since it seems to sound like it requires toil on our part, although I doubt the authors saw it that way.