When Becky (my oldest daughter) was newborn and still in the maternity ward at the hospital I brought a big Bible and held it up before the window. I shouted through the window, "Becky, this is the Word of God." and I waved the Bible from side to side. (I am not sure that she was impressed!)
The first day she was home from the hospital I put her on the floor, got the Bible, and told her how to be saved. I did this every week even when she was an infant. I am not sure when the moment was that salvation's plan first dawned upon her, but I am sure that she knew how to be saved, for regularly I took the Bible, went to her crib, and told her about Adam and Eve, the depravity of man, the wrath of God, God's plan of salvation, the atonement, the resurrection, etc. I wanted to be sure she associated her daddy with a black book called the Bible and in her subconscious mind was registered God's plan of salvation. How important this is in the life of a child.