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, , is His Slave and Messenger.
The sick person who should give the expiation is the one whose disease is incurable, but the sick person who is expected to be cured must make up for the missed fasting days when he is cured. Allaah The Almighty Says (what means): {So whoever among you is ill or on a journey [during them] - then an equal number of days [are to be made up].} [Quran 2:184]
Consequently, if there is no hope that you will be cured, then you would be required to feed a needy Muslim person for each missed fasting day. Allaah The Almighty Says (what means): {And upon those who are able [to fast, but with hardship] - a ransom [as substitute] of feeding a poor person [each day]. And whoever volunteers excess - it is better for him. But to fast is best for you, if you only knew.} [Quran 2:184]
Ibn ‘Abbaas said that this verse is not abrogated, but is rather meant as a concession for old men and women who have no strength to fast as well as sick people who are not expected to be cured, so they should feed one poor person for each day of fasting (instead of fasting). This is the opinion of the majority of scholars except Imaam Maalik .
Considering this, you should know that it is not permissible for you to give the expiation for a fasting day until you already break your fast on that day, i.e. after the crack of dawn, because fasting is not obligatory for you before that time.
Hence, you have two options:
It is also permissible to give the expiation for the whole month to a single needy person because each day is considered an independent act of worship. This ruling was expressly stated by Al Mardaawi in "Al Insaaf" and also by the Permanent Committee for Research and Fatawa.
In brief, it is not permissible for you to give the expiation at the beginning of Ramadan, and it is permissible to give the expiation for the whole month to a single needy person or a four-member family.
The ransom is a Mudd (750 g) of the common food of the country for each missed fasting day. However, if you give half a Saa' (one and half Kg) it would be better to avoid the difference of opinion amongst scholars (to be on the safe side).
Allaah Knows best.