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.
It is an obligation before dividing the inheritance to pay back the debt that the deceased owes to people, because the debt takes precedence over the right of the heirs in the inheritance. After paying the debt, then his will be looked at. If the five acres for which he made a will do not exceed a third of the inheritance, then it is an effective will, which will be taken by the granddaughter for whom he made the will, as it is a will for a non-heir that does not exceed one third. However, if the will exceeds one third of the inheritance, then only one-third of it is effective and whatever exceeds a third, the person for whom the will is made does not take it except with the consent of all other heirs.
After paying off the debts and deducting the will, the heirs will divide the remaining inheritance between them according to the Book of Allaah and the Sunnah (tradition) of the Prophet .
The wife who died before him is not entitled to anything in the inheritance.
Therefore, if the deceased did not leave any other heirs except those mentioned in the question, then his mother gets one-sixth as her legal share due to the existence of direct heirs (children) as Allaah The Almighty Says (what means): {And for one’s parents, to each one of them is a sixth of his estate if he left children.}[Quran 4:11] His wife gets one-eighth as her legal share due to the existence of the children (direct heirs); Allaah The Almighty Says (what means): {But if you leave a child, then for them [i.e. the wives] is an eighth of what you leave, after any bequest you [may have] made or debt.}[Quran 4:12]
The remainder should be divided amongst the son and the daughter by Ta’seeb (by virtue of having a paternal relation with the deceased and not having an allotted share, so they get what is left after the allotted shares have been distributed). The male gets twice the share of the female as Allaah The Almighty Says (what means): {Allaah instructs you concerning your children [i.e. their portions of inheritance]: for the male, what is equal to the share of two females.}[Quran 4:11]
However, the full brothers and the full sisters of the deceased do not get anything from the inheritance because they are prevented by the existence of the son.
Therefore, the inheritance should be divided into 216 shares, the mother gets one-sixth, which is 36 shares, the wife gets one-eighth, which is 27 shares, the son gets 34 shares and the daughters get the remaining 17 shares each.
And Allaah Knows best.