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. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If the car is not road worthy because of its very bad condition or bad tyres, or that the car is road worthy but the driver was driving at a speed beyond which he could not control the car or the like, then the man deserves the Diyyah (blood money) for his son and compensation for his and his wife's injuries. He is not permitted to take more than this. The Diyyah should be paid by the driver's 'Assabah, who are the blood male relatives from his father's side with the exception of his father and grandfather, and his sons and grandsons. The closest relative is put in priority over others, i.e. the brothers come before the uncles and so forth. The evidence about this is that a woman from the tribe of Huthayl killed another woman from the same tribe, each of whom had a husband and children, so the Prophet ruled that the Diyyah of the dead woman should be paid by the blood male relatives of the killer while her husband and children were exempted from paying any Diyyah; by analogy the father is like the son. Furthermore, the company where the driver works could pay the Diyyah of the son on behalf of the driver.
Allaah Knows best.