While most of us have wised up about the reliability of commercials, many adults are still quick to believe something simply because another person says (or writes) it's so. Countless emails get passed around cyberspace claiming to be a warning of some sort that will protect you from harm and urging you to pass it along to everyone you know. There are places on the internet where you can verify if that information is correct or not but few people either know where to verify it, how to verify it, or take the time to verify it.
When it comes to scripture we should not simply take another person's word (or written work), for what the Bible says or means, and we should be teaching our children not to either. We should be in the habit of verifying scripture ourselves, and teaching our children how to do the same, prayerfully researching it out. A concordance and bible dictionary are very useful tools for helping to understand scripture as well. We gain more insight into and understanding of God's Word when we look at the original text and it's meaning.
And the people of Berea were more open-minded than those in Thessalonica, and they listened eagerly to Paul’s message. They searched the Scriptures day after day to see if Paul and Silas were teaching the truth. Acts 17:11 (emphasis mine)
Why is it important to know scripture for ourselves? First and formost is that studying God's Word for ourselves is the best way to develop a deep, intimate relationship with Jesus.
Another reason is that there are those who would deliberately teach wrong doctrine to draw us and/or our children into their "religion" or cult. The best way to spot a counterfeit is to know the original.
Even with people we can trust, our friends, parents, pastors, reputable authors, etc, we need to remember that they can make mistakes. We are imperfect humans and we all make mistakes. As teachers of God's Word, we are held to a high standard to teach it accurately. So it is important that we use reliable references, research out what we are being taught, and teach our children to do the same. We need to keep in mind that popularity and opinion are not proper guages for reliablity, accuracy is.
One way to teach children to develop the habit of verifying scripture is to have them verify the scriptures and meanings you are teaching them. Who knows, they might come back and teach you something you didn't know.
Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth. 2 Timothy 2:15 (emphasis mine)
Let not many of you become teachers, my brethren, knowing that as such we will incur a stricter judgment. James 3:1
Preach the Word; be prepared in season and out of season; correct, rebuke and encourage—with great patience and careful instruction. 2 Timothy 4:2 (emphasis mine)
You must teach what is in accord with sound doctrine. Titus 2:1 (emphasis mine)