Does the presence of her son next to his deceased mother affect the angels' taking of her soul? And is it permissible, according to Sharia, to distribute a small amount of the deceased's money to children and pay the remainder as a fee for building her grave without the knowledge of the other heirs, or is it considered an inheritance that must be divided?

The angels who do not enter the house of a person in a state of janaba (major ritual impurity) are the angels of mercy, not the angels appointed to seize souls, nor the recording angels (Kiraman Katibin) or the guardian angels (Hafadha). The janaba mentioned refers to one who is negligent in performing ghusl (definition) (ritual bath), not just any person in a state of janaba, as evidenced by the Prophet, peace and blessings be upon him, who would visit his wives and perform a single ghusl. As for the money left by the mother, it is first used to cover her burial expenses, and then the remainder is distributed among the heirs. It is not permissible to dispose of the money by giving some to the minors without the permission of the other heirs; rather, they must be informed, and if they agree, then it is permissible, otherwise, their right must be given to them.