For many parents, this is a big fearful question. Am I doing it right? Am I sharing too much, too little, not correctly, how much do they understand?
When my daughter was born, I was utterly fascinated by this tiny human with her big soulful eyes. I found myself staring into those eyes, feeling that she knew so much more than I did! I felt overwhelmed by the thought that I had to teach her everything and that she is going to live her life, with all this knowledge that I gave her: and she will believe every word that comes from my lips.
What a great responsibility!
One of the big questions was: when is old enough to start talking about God?
The simple answer is: from even before they are born, every day and in everything you do!
Never stop talking about God and what God is now doing in your life. As you share your thoughts with God, share them with your children.
This is the only way they will understand that "The Gospel" is a relationship with the Almighty. If they see your relationship, they will also participate in that relationship.
God is as much a part of your family as you are, and the sooner your child sees and understand that, they will just accept God's presence in their lives in the same way they do yours.
So! Start sharing your innermost thoughts with your children, you will never regret it and your relationship with your children and with God will grow with abundance!