I have to say this: the name of the ministry "No Greater Joy" is based on a false understanding of the book of 3rd John. "I have no greater joy than to hear that my children are walking in the truth." has NOTHING to do with parenting if you read it in context.
The book is a personal letter from John to Gaius. The theme of 3 John is steadfastness in the face of opposition. The recipient of the letter, Gaius, faces a troublemaker named Diotrephes.
I don't think there's anything wrong with quoting the verse and applying it to child-rearing, as long as the truth that we are referring to is the TRUTH. And the truth of the gospel is that Jesus came and died, that He showed mercy to the undeserving, that He loved His children with an everlasting love.
Parenting is a difficult calling. The only way to do it well is to rely on the Holy Spirit, not on man-made philosophies. When you have a rebellious child, cry out to God. When you have a disobedient child, cry out to God. Ask Him to guide you. Ask Him for wisdom. Ask Him to help you.