With our four children, who now are adults, my wife used childrens Binbles, and Bible story books. You plant the seed (the Word of God) and gradually nurture the child in spiritual growth, until one day they will ask you how to have Jesus live in us. You most likely will find this matake until they are in their teens to fully understand salvation. Again this may take sever times that the awaken to what Jesus is all about. A couple of our children were baptised twice, because they were not sure they fully understood what they were doing. Being baptised several times is not going to harm a thing. I have seem adults rededicate their life by rebaptising them over again. What ever it takes for people to bring their spiritual conviction to mature.
Bless you and your youngen'.s