Praise be to Allah.
We ask Allaah to help you and guide you, and to compensate you with something better if you leave your job, and to bless you with a righteous husband who will be a delight to you.
If the marriage contract is done with the consent of both parties and in the presence of the woman’s wali (guardian) and two witnesses, then it is a valid marriage, whether the consummation takes place immediately afterwards or it is delayed for a long time or a short time.
The Messenger (peace and blessings of Allaah be upon him) did the marriage contract with ‘Aa’ishah when he was in Makkah, and he consummated the marriage with her three years later. Narrated by al-Bukhaari (3894) and Muslim (1422).
It is better for him to try and convince his parents of this marriage, because that will be beneficial for him and for you and your children. He should try not to do this marriage without the agreement of his family, so that it will not be a cause of never-ending disputes and arguments or have a bad effect on your family life.
It should be noted that it is not permissible for you to form a relationship with this young man, and that the fiancé is a stranger (non-mahram) to his fiancée until the marriage contract is done.
And Allaah knows best.