Question: In the case of a child then, you would believe that even though they may do many things that seem to be sinful, they are not considered a sinner until they knowingly are going against God himself. Right?
Answer: With a child I hold that the Scriptures teach that from birth they are imputed righteous by God, but are not converted. Also, that a time will come in their life where they will knowingly transgress the law of God and will experience guilt and condemnation that will not be relieved by having that act revealed and receiving correction by their parents.
At this point, they are separated from God, or are spiritually dead or what the Bible calls “dead in trespasses and sins” (Eph 2:1). It is common for children to feel guilt for wrong actions, but this will pass when their acts have been revealed and they have received correction for the offense.
One of the signs that a child has passed from innocence into the age of accountability is when wrong actions have been revealed and received correction for, but the guilt the Child experiences does not leave. At this point, they need more than forgiveness and correction from their parents: they need forgiveness and conversion.
Paul brings this out in Romans 7 when he discusses when this happened to him. “For I was alive without the law once: but when the commandment came, sin revived, and I died” (Rom 7:9).
This is referred to many as “the age of accountability”. Typically it will be from the age of 8 to 12, but can be as early as 5 or 6, and if the person is mentally-challenged they many never come to the age of accountability.
I suggest you read the article on Leading Your Children to Christ.