Entrusting someone with money and bequeathing it to charity after death while having five daughters and a lesser amount of money than stated

Q: My mother-in-law gave me a sum of 49,000 riyals and asked me not to inform anybody of it. She trusted me with this money to pay in charity on her behalf after her death. I would like to inform you that this old lady has no relatives except five married daughters and none of them was living with her at that time. I fear that if I executed her will, I would do wrong to the daughters, because they are entitled to that money as heirs of their mother. Kindly give me your Fatwa in this regard. May Allah reward you the best. Should I pay (Part No. 16; Page No. 306) all the money in charity or only some of it, or what should I do? I want to implement the will, but I am afraid that I may deny the daughters their legal share in their mother's money. Bear in mind that the mother did not earn that money from her husband; rather, from the social fund and some benevolent people. Furthermore, after the mother's death, the five daughters found 27,000 riyals and they paid some of it in charity and the other to a Masjid (mosque). I ask Allah, then Your Eminence to kindly give me your Fatwa. May Allah reward you on my behalf and this old woman.

A: The mentioned will is not valid except for a third of the money, and the rest should go to her heirs, unless they permit to pay all the money in charity on her behalf. Therefore, you should inform her heirs about this will. If they approve of the will, do it as written; otherwise you should only pay a third in charity. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.