The Catechism of the Catholic Church, states:

As regards children who have died without Baptism, the Church can only entrust them to the mercy of God, as she does in her funeral rites for them. Indeed, the great mercy of God who desires that all men should be saved, and Jesus’ tenderness toward children which caused him to say: ‘Let the children come to me, do not hinder them,’ allow us to hope that there is a way of salvation for children who have died without Baptism. (n.1261)

We also have an understanding of the notion of “baptism by desire” (cf. Catechism, no. 1259-60) in which it is taught that people who die while unbaptized are supposed to have been baptized by their “explicit desire” to receive this sacrament. This may also apply to children whose parents intended to baptize their child after birth.

The Catechism also states, “God has bound salvation to the sacrament of Baptism, but he himself is not bound by his sacraments” (n. 1257). Put another way, “Baptism is necessary for salvation for all those to whom the Gospel has been proclaimed and who have had the possibility of asking for this sacrament.” (Compendium of the Catechism of the Catholic Church, no. 261)

God is all powerful and also merciful. While the Church cannot definitively say that your child(ren) are in Heaven, she is compassionate and very hopeful regarding your child(ren)’s salvation. 

For further reading on the subject of unbaptized infants, you may like to read International Theological Commission’s The Hope of Salvation for Infants Who Die Without Being Baptised.