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.
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 because of the existence of the children (direct heirs) of the deceased; Allaah 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 of the deceased; Allaah 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 two sons and the two daughters 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 twice the share of the female as Allaah 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]
Therefore, the inheritance should be divided into 144 (one hundred and forty four) shares; the mother gets one-sixth of it, which is 24 shares, the wife gets one-eighth, which is 18 shares, and each son gets 34 shares, and each daughter gets 17 shares.
Allaah Knows best.