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 the father wrote his property in his wife’s name not as a gift for her but merely to make it in her name in government records without making her the actual owner, then doing so does not affect the status of his ownership of that property. Rather, it is to be inherited and divided, after his death, among all of his heirs, each taking his lawfully allocated share.
Likewise, if he gave it to your mother as a gift but she did not receive it (into her possession) before he died or if he willed his wealth to her after his death, then none of that is fulfilled except with the consent of the heirs, provided they are mature adults.
Hence, if the heirs are only those mentioned in the question, and there is no heir by Ta'seeb (male paternal relative of the deceased, like a paternal cousin and so forth), then the estate is divided into eight shares. The wife (your mother) receives one share (one eighth of the inheritance) and each of the seven daughters receives one of the seven remaining shares, i.e. after apportioning the obligatory amounts to the daughters (two thirds of the inheritance), the remaining balance is further given to them on top of what was due (i.e. they get the whole remaining inheritance, as there is no other heir).
As for the daughter who died before the estate was divided, her share is divided among her own heirs, i.e. her mother, son, daughter and husband if she died while her husband was alive.
Your mother is not allowed to divide the estate into nine parts, giving one part away as charity for the deceased, unless this was specified in his will or if all of the heirs (while mature adults) consent to this. Otherwise, those of them who want may take from their own allotment, as they please, and nothing is taken from those who do not want and those who have not yet reached maturity.
So the amount allocated to the deceased daughter must be divided among her heirs as we explained, and the mother has no right to give it to the son alone. Rather, your mother may take her own portion and give it to whomever she wishes of the heirs or make it a continuous charity on her husband’s behalf.
The above is if the deceased did not give his property as a gift (transferring the status of ownership) to his wife before he died, and if the registration of his wealth in her name was not a “gift.”
As for if he gave his property to her as a gift before his death and she actually possessed it as her own property, then she may divide it into nine parts as was mentioned in the question. This is because it is her own wealth and there is no harm in dividing it as such. However, such division is not binding unless each actually receives his/her share before the mother's death.
Allaah Knows best.