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 heirs are only those mentioned in the question and the deceased did not leave any other heir, then it is the wife, the son and the daughter who inherit amongst them only, the other relatives do not inherit due to the existence of the son, in which case, the wife gets one-eight as her legal share due to the existence of the children (direct heirs) 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 son and the daughter according to their legal share; 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 24 (twenty four) shares; the wife gets one-eighth of it, which is 3 shares, and the son gets 14 shares, and the daughter gets 7 shares.
Allaah Knows best.