JOEL - We know that all children who die before the age of accountability will inherit the Celestial kingdom(D&C 137:10). And we know that those who do inherrit the Celestial kingdom will come forth in the morning of the first resurrection(D&C 76:64, 70).
Speaking of those who live during the Millennium God said:
"And the earth shall be given unto them for an inheritance; and they shall multiply and wax strong, and their children shall grow up without sin unto salvation." (D&C 45:58)
If as the scriptures say these Celestial children are going to be resurrected first and "grow up" during the millennium, there is going to need to be someone there to raise them. If their parents were sealed in the temple, they will be able to continue their eternal family relationship.
President Joseph Fielding Smith said:
“The Lord will grant unto these children the privilege of all the sealing blessings which pertain to the exaltation. We were all mature spirits before we were born; and the bodies of little children will grow after the resurrection to the full stature of the spirit, and all the blessings will be theirs through their obedience, the same as if they had lived to maturity and received them on the earth. .” (Doctrines of Salvation, 2:54.)
Joseph Smith taught the doctrine that the infant child that was laid away in death would come up in the resurrection as a child; and, pointing to the mother of a lifeless child, he said to her: ‘You will have the joy, the pleasure, and satisfaction of nurturing this child, after its resurrection, until it reaches the full stature of its spirit.’ There is restitution, there is growth, there is development, after the resurrection from death. I love this truth. It speaks volumes of happiness, of joy and gratitude to my soul. Thank the Lord he has revealed these principles to us.” (Gospel Doctrine, pp. 455-56.)
If Joseph Smith said it and other prophets have taught it, that's official enough for me. My wife and I are looking forward to the time when we will be able to finish raising our own first daughter(Janna) who died at 5 weeks of age. I am hoping it will be a lot easier than it has been with her little sister(now a teenager) :-)
When our children were younger we had a Family Home evening chart that hung on our wall in the family room. On that chart was listed each name in the family and next to each name would be placed little pictures, representing the assignment that each one would have for the upcoming Family night.
There was a picture of someone saying a prayer, or someone giving a lesson, or a picture of an apple pie representing the all-important treat. Of course those pictures would rotate each week. But next to Janna's name was permanently placed a picture of a lighthouse. Janna's sole responsibility for every family night and indeed for the rest of our lives was to be what we called our Celestial beacon. We know she will be in the Celestial kingdom and we want to be with her there and be there for her when we are all resurrected and continue as an eternal family.