Is it sufficient to pay the expiation for an oath to a family whose number is unknown?

This expiation is not sufficient according to the majority of jurists (Malikis, Shafi'is, Hanbalis) because they do not permit giving money as expiation for an oath. What is obligatory is feeding ten poor people, or clothing them, or freeing a slave. If one is unable to do so, then fasting three days.

It is a condition that the expiation be given as food or clothing to ten poor people. According to the Hanafis, it is permissible to give the value [in money], and it is permissible to feed one poor person for ten days, but it is not permissible to give the food for ten days to one poor person on a single day. What you have given in money may be sufficient according to the Hanafis, based on the number of that family.

The view of the majority is more cautious and more absolving of responsibility. Therefore, the expiation should be re-issued in the manner mentioned (feeding, clothing, freeing a slave, or fasting).