All your children shall be taught by the Lord, and great shall be the peace of your children. Isaiah 54:13
Frequently the more you witness to your children, the farther they seem to pull away from the Lord. An idea is given in Luke 10:2, which tells you are to pray that the Lord of the harvest will send forth laborers into His harvest. God wants you to frequently ask Him to send others to your children.
Instead of pointing out the things they are doing wrong, compliment them on what they are doing right. As their hearts start to soften, they will be more willing to accept what others tell them about Jesus.
Expect God to honor His Word by teaching them what they have missed because of the humanistic educational system and news media that is controlling much of the World. Thank Him for the answers to come.