JOEL - The spirits of all children who die before the age of accountability go to Paradise in the Spirit World like any other righteous mortal who dies. These children do not require baptism as Jesus indicated when He said:
"But Jesus said, Suffer little children, and forbid them not, to come unto me: for of such is the kingdom of heaven." (Matt. 19:14)
Joseph Smith’s vision of the celestial kingdom (D&C 137) makes it clear that the baptism in this life of infants and little children is not required. They are saved through the atonement and because they are free from sin. Still in an inocent state when they enter Paradise, they will probably not need to be reeducated on Gospel principles that they already knew when they were in the pre-earth life. Speaking about this Bruce R. McConkie said:

"We understood and knew the gospel plan and shouted for joy at the privilege of getting our mortal bodies as part of that great plan of salvation. Returning pure and spotless to their Maker, children who in reality are adults will again have that gospel knowledge which once was theirs." (Ensign, Apr. 1977, 3)

They may even be enlisted to help preach the Gospel to those in Spirit Prison, who because of their behavior and experiences on earth, will have forgotten all that they knew when they were in the pre-existance. President Woodruff once learned from the Lord that his son, who died as a child, "was needed in the spirit world to preach the gospel and labor among those relatives there". (Crowther, Life Everlasting p.205)
It is possible that at some future time, perhaps during the Milennium, that they will be baptized, to fulfill all righteousness as Jesus did, and receive temple endowments. But precisely what the Lord will require in the form of ordinances, or other requirements, for spirits who died as infants or children on earth in order to receive exaltation has not been revealed. It is certain that we do not currently endow children who die before accountability nor do we seal them to a spouse. But this does not mean that the blessings of these latter ordinances are unavailable to them. President Joseph Fielding Smith once said:

"The Lord will grant unto these children the privilege of all the sealing blessings which pertain to exaltation.
We were all mature spirits before we were born, and the bodies of little children will grow after 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.
The Lord is just and will not deprive any person of a blessing, simply because he died before that blessing can be received. It would be manifestly unfair to deprive a little child of the privilege of receiving all the blessings of exaltation in the world to come simply because it died in infancy." (Doctrines of Salvation, Vol. 2)