As parents, more than anything else, we must set a godly example for our children. They will not follow where we do not lead. We must also teach them and train them in the whole counsel of God, so they will know the truth, the whole truth, and nothing but the truth. This is how we mark our children for God. If we do not do this, the enemy stands at the door, just waiting to make them his.
Looking back on the last couple of decades in the American church, most kids who grew up in church have no knowledge of or experience with the power of the Holy Spirit or a depth of understanding from God's Word. Their parents and their churches turned them out into the world with no real, practical spiritual foundation or discernment. They can tell you all about the latest blockbuster movie or the latest YouTube video that's gone viral, but they don't know what really pleases God.
Thank God the Bible gives us hope! "Though its roots have grown old in the Earth and its stump decays, at the scent of water it will bud and sprout again like a new seedling" Job 14:8-9.