All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
If your father-in-law resolved to do ‘Umrah after visiting Madeenah without hesitation, then it is obligatory upon him to assume Ihraam from Thul Hulayfah, the Meeqaat of the people of Madeenah i.e. Abyaar ‘Ali, and it is not permissible for him to delay assuming Ihraam until Jeddah, for the Prophet, sallallaahu ‘alayhi wa sallam, said regarding Meeqaats: “… and these (Meeqaats) are for the people at those very places, and besides them for those who come through those places with the intention of performing Hajj and 'Umrah; and whoever is living within these boundaries can assume lhraam from the place he starts from…” [Al-Bukhari and Muslim]
However, if he was not resolved to do ‘Umrah or hesitated whether to do it or not, he is not obliged to assume Ihraam from Thul Hulayfah, and he can go to Jeddah, and whenever he is resolved to do ‘Umrah, he can assume Ihraam from it, for the Prophet, sallallaahu ‘alayhi wa sallam, said in the Hadeeth stated above: “And whoever is living within these boundaries can assume lhraam from the place he starts from.”
Allaah Knows best.