Much of what happens in the Celestial kingdom has not been revealed to us, and likely won't be revealed until we actually get there. I think the Lord knows that, as mortals, we are not prepared for the knowledge of the mysteries of the Kingdom. Not only that, but revealing all things would leave little room for us to excercise faith, which is how growth occurs. A simple answer to a child's questions could be "We don't know, but if we are good we will find out someday."