In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Thank you for your question, we implore Allah to reward us all for whatever we do for His sake.
Muslim parents should take special care to bring up their children according to the teachings of Islam. There is nothing wrong, as far as Islam is concerned, with children knowing about other faiths. However, their parents should instill Islamic manners in them and teach them that Islam is the right path.
If a Muslim man marries a non-Muslim woman, then their children should be raised up as Muslims. This is a matter that should be stipulated before marriage in order to keep the home intact from the dire consequences of divorce.
In all cases, divorce should be the last resort, as the Prophet (peace and blessings be upon him) is reported to have said, "Of all things lawful, divorce is the most hated in the sight of Allah" (Al-Bukhari).
Responding to the question, Sheikh Muhammad Al-Mukhtar Al-Shinqiti, director of the Islamic Center of South Plains in Lubbock, Texas, states the following:
There is a difference between knowing faith and adopting it as a way of life. Knowledge of other than one's faith is something good, even though the person might not embrace it. But to follow a religion is something serious that requires a lot of work from Muslim parents to raise their children following the right belief in God.
Almighty Allah says, [Or were ye present when death came to Jacob, when he said unto his sons: What will ye worship after me? They said: We shall worship thy God, the God of thy fathers, Abraham and Ishmael and Isaac, One God, and unto Him we have surrendered] (Al-Baqarah 2:133). So Jacob was only concerned about the faith his children should follow after his death, that is to believe in Allah alone and not to associate any partners with him.
In a hadith, the Prophet (peace and blessings be upon him) highlighted the responsibility of parents towards raising their children: "Every child is born a Muslim, then his parents make him a Jew, a Christian, or Magian" (Al-Bukhari).
Therefore, even if a Muslim man is married to non-Muslim woman, he must raise his children as Muslims, and he should be sure to stipulate this before marriage.