Will a child that commits suicide go to heaven?
Catechism of the Catholic Church:
2282 …Grave psychological disturbances, anguish, or grave fear of hardship, suffering, or torture can diminish the responsibility of the one committing suicide.
2283 We should not despair of the eternal salvation of persons who have taken their own lives. By ways known to him alone, God can provide the opportunity for salutary repentance. The Church prays for persons who have taken their own lives.
But for a person to be guilty of mortal sin, the individual must know the act is mortally sinful and freely chooses it. People who commit suicide are usually suffering from some kind of emotional or psychological condition that at a point overwhelms them and thereby limits their ability to be realistic about the issues they face or the ‘remedy’ they choose, in this case ending their lives.
It is even more so for children who even on a normal day do not understand the full implication of their actions.
The other thing to remember is that God is a Father, Our Father. He loves us greatly and wants us to be saved. It is very safe to believe that God will embrace such a child with great love and compassion.