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.
Inheritance is a grave matter. Allaah The Exalted did not leave its division to a sent prophet or a close angel, but He laid down its rules Himself, apportioning the divisions accordingly. Allaah defined for each heir his share of inheritance: This includes the wife, the sons, the daughters, and so forth. Allaah The Exalted said (what means): {Allaah instructs you concerning your children: for the male, what is equal to the share of two females.} [Quran 4:11] He also said (what means): {And for the wives is one fourth if you leave no child. But if you leave a child, then for them is an eighth of what you leave, after any bequest you [may have] made or debt.} [Quran 4:12]
As for the will of a man that he gives his inheritance to his children after his death, such is a bequest for an heir, which is not binding. It can only be executed if the remaining heirs agree to it. The Prophet, sallallaahu ‘alayhi wa sallam, said: “Verily Allaah has given every rightful person his right; so there is no bequest for an heir.” [Ibn Maajah - Al-Albaani graded it Saheeh (sound)]
Kindly refer to Fataawa 116588 and 94685 regarding there being no bequest for an heir.
Based on this, if the wife is content with executing the bequest, and she is a mature adult, then so be it. But if she is not content or she is a minor, then she has the right to take her legitimate share of inheritance.
For more benefit, please to Fataawa 139527 and 156799.
Allaah Knows best.