A word on sin to all Christians, and especially parents, from J.C. Ryle:
[M]en try to cheat themselves into the belief that sin is not quite so sinful as God says it is, and that they are not so bad as they really are. You may see it in the tendency even of believers to indulge their children in questionable practices, and to blind their own eyes to the inevitable result of the love of money, of tampering with temptation, and sanctioning a low standard of family religion. I fear we do not sufficiently realize the extreme subtlety of our soul's disease. We are too apt to forget that temptation to sin will rarely present itself to us in its true colours, saying, "I am your deadly enemy, and I want to ruin you forever in hell." Oh, no! sin comes to us, like Judas, with a kiss; and like Joab, with an outstretched hand and flattering words. The forbidden fruit seemed good and desirable to Eve; yet it cast her out of Eden. The walking idly on his palace roof seemed harmless enough to David; yet it ended in adultery and murder. Sin rarely seems sin at its first beginnings. Let us then watch and pray, lest we fall into temptation. We may give wickedness smooth names, but we cannot alter its nature and character in the sight of God. Let us remember St. Paul's words: "Exhort one another daily, lest any be hardened through the deceitfulness of sin" (Heb. 3:13). It is a wise prayer in our litany, "From the deceits of the world, the flesh, the devil, good Lord, deliver us."
from Holiness by J.C. Ryle, p. 9.