What are the legitimate ways to marry a divorced Canadian woman with children, who wishes to marry a Muslim man?

You must repent to Allah for the leniency in the relationship that preceded the engagement. As for marrying her: 1. If she is Muslim and her family are Muslims: Ask for her hand from her family, and her legal guardian (her father, brother, or closest male relative) should marry her off. 2. If she is Muslim and her family are disbelievers: A disbeliever has no guardianship over a Muslim woman. In this case, her closest Muslim male relative should marry her off. If none exist, the Imam of the mosque or the director of the Islamic center should marry her off.

Before proceeding with the marriage, ensure your financial and social capability to bear the responsibility towards both wives, and that it will not cause harm to your first family. If circumstances do not permit, or if harm is expected, then marriage is not advisable.