How is the estate of a deceased husband distributed among the children, and what should the wife do with the eldest, mature son whom she fears will squander his share of the inheritance?

The deceased's estate is divided among the heirs according to what is stated in the Quran and Sunnah (definition). The general rule is that a mature, sane individual receives their share, unless their foolishness is proven, in which case they are interdicted by a judge.

As for underage heirs, they are interdicted for their own benefit. Their guardian is their father's executor, or a judge if the father did not appoint one. Governmental institutions for safeguarding orphans' wealth assume the role of the judge.

The matter of the inheritance must be presented to the Sharia (definition) court to divide it and to consider how to preserve the wealth of minors and who deserves to be interdicted.