Is the amount of rice given by the father to feed the poor sufficient and valid as expiation for the days he missed fasting due to his illness, and is the time of giving it out appropriate?

If the father's illness is expected to be cured, then feeding the poor is not sufficient for him, and he must make up the days he missed. If his illness is not expected to be cured, then he must pay a fidyah (definition) by feeding one poor person for each day he missed. The amount of the fidyah according to the Shafi'is is a mudd of food, and according to the Hanbalis, it is a mudd of wheat or half a sa' of other food. As for the time of paying the fidyah, scholars have differed on this, and the preponderant opinion is that it is not permissible to pay it in advance before the night of the day he will break his fast.