We may think that we are showing them mercy or grace, but if we are not clear and careful we are actually teaching them tolerance of sin, disobedience, and rebellion. This is not to say that there is never a time to show mercy, but it needs to be clearly communicated that this is what happened this one time and why. The rule of obedience must be established first before the mercy or grace can be shown effectively.
2 Peter 3:9-10 says, "The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. (10) But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up." As Fathers we are in the position of showing God to our children. If they see us slack in this area they will believe God is slack as well, and He is not. There are eternal consequences for your children’s souls at stake, so let’s be diligent about it.