The following excerpts from an article written for The Ensign by Elder Bruce R. McConkie is the clearest statement on the salvation of little children that I have found.
Bruce R. McConkie, “The Salvation of Little Children,” Ensign, Apr 1977, 3
Nowhere does the Easter message of resurrection ring so triumphant.
Among all the glorious gospel verities given of God to his people there is scarcely a doctrine so sweet, so soul satisfying, and so soul sanctifying, as the one which proclaims—Little children shall be saved. They are alive in Christ and shall have eternal life. For them the family unit will continue, and the fulness of exaltation is theirs. No blessing shall be withheld. They shall rise in immortal glory, grow to full maturity, and live forever in the highest heaven of the celestial kingdom.
What is a child and who are children?
A child is an adult spirit in a newly born body, a body capable of growing and maturing according to the providences of Him whose spirit children we all are. Children are the sons and daughters of God. They lived and dwelt with him for ages and eons before their mortal birth. They are adults before birth; they are adults at death.
Are children tainted with original sin?
Absolutely not. There is no such thing as original sin as such is defined in the creeds of Christendom. Such a concept denies the efficacy of the atonement. Our revelation says: “Every spirit of man was innocent in the beginning”
Are all little children saved automatically in the celestial kingdom?
To this question the answer is a thunderous yes, which echoes and re-echoes from one end of heaven to the other. Jesus taught it to his disciples. Mormon said it over and over again. Many of the prophets have spoken about it, and it is implicit in the whole plan of salvation. If it were not so the redemption would not be infinite in its application. And so, as we would expect, Joseph Smith’s Vision of the Celestial Kingdom contains this statement: “And I also beheld that all children who die before they arrive at the years of accountability are saved in the celestial kingdom of heaven.” (D&C 137:10)
Will they have eternal life?
Eternal life is life in the highest heaven of the celestial world; it is exaltation; it is the name of the kind of life God lives. It consists of a continuation of the family unit in eternity. Joseph Smith taught, “Children will be enthroned in the presence of God and the Lamb; … they will there enjoy the fulness of that light, glory, and intelligence, which is prepared in the celestial kingdom.” (Teachings of the Prophet Joseph Smith, p. 200.).
Will children be married and live in the family unit?
Certainly. There can be no question about this. If they gain salvation, which is eternal life, which is exaltation, it means that they are married and live in the family unit.
Why do some children die and others live? Are those who die better off than those who remain in mortality?
President Joseph Fielding Smith once told me that we must assume that the Lord knows and arranges beforehand who shall be taken in infancy and who shall remain on earth to undergo whatever tests are needed in their cases. This accords with Joseph Smith’s statement: “The Lord takes many away, even in infancy, that they may escape the envy of man, and the sorrows and evils of this present world; they were too pure, too lovely, to live on earth.” (Teachings, pp. 196–97.)
Will children ever be tested?
Absolutely not! “Satan cannot tempt little children in this life, nor in the spirit world, nor after their resurrection. Little children who die before reaching the years of accountability will not be tempted.” (Doctrines of Salvation, 2:56–57.) Such is the emphatic language of President Joseph Fielding Smith.
What is the age of accountability?
In our revelation the Lord says, “They cannot sin, for power is not given unto Satan to tempt little children, until they begin to become accountable before me.” (D&C 29:47.) There comes a time, however, when accountability is real and actual and sin is attributed in the lives of those who develop normally. It is eight years of age, the age of baptism. (D&C 68:27.)
What about the mentally deficient?
It is with them as it is with little children. They never arrive at the years of accountability and are considered as though they were little children.
When and with what stature will children be resurrected?
Because they will receive a celestial inheritance, they will come forth in the first resurrection, President Joseph F. Smith said: “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.’
What, then, of this glorious doctrine concerning the salvation of children?
Truly it is one of the sweetest and most soul-satisfying doctrines of the gospel!
The Fairest Gem 