Permissibility of the trustee taking from the returns what they need in return for their work

Q: My husband died and appointed me as an executor of his bequest. This is the text of the bequest: "I bequeath my wife Fatimah bint Abdullah Al-`Amar one third of all that I have, including shares, money, companies, real estate, land and moveable and immovable things whether in Kuwait or abroad. This money should be spent on adult and minor needy persons from among my offspring, males and females. Moreover, if Fatimah is in need of anything from this third, she will be permitted to receive what she needs of food and so on." The testator, Sayid Abdul-Razzaq permitted his wife to appoint a righteous executor to succeed her from among their sons.We would like Your Eminence to give us a detailed Fatwa that contains an elaboration on the following points: (Part No. 16; Page No. 402) 1- It is mentioned in the text of the bequest: "My needy offspring should receive from the revenue of this third." Is this bequest confined to doing charitable deeds only or can the wife of the testator and his children benefit from it in case of their need? Are they more worthy of benefiting from the revenue of this third than poor and needy Muslims in general? Is this bequest confined to needy persons from among the heirs of the testator only and therefore can not be spent on other charitable deeds? Should this bequest be limited to doing charitable matters only as there is no bequest for an heir? Does this mean that heirs cannot benefit from this third?2- Does this bequest apply to adult and minor children in this generation and the next? If this bequest is confined to this generation only, what is the ruling on the revenue that remains after their death? Who will be permitted to make use of this money?3- What is the meaning of "the need" that was mentioned in the bequest? Does the word need apply only to those who were needy at the time of the death of the testator or for other times in the future? Can we nullify the bequest under the pretext that there is no minor or needy person at the present time? Moreover, my husband was very benevolent and helpful to the needy. He was keen to continue performing charitable deeds after his death. (Part No. 16; Page No. 403) I hope to receive a Fatwa concerning the content of this bequest as soon as possible because I will not begin executing this bequest until I receive a detailed answer for my questions according to the understanding of the scholars. I hope you can answer my question soon. I ask Allah to make you useful to His religion and Shari`ah (Islamic law). He is All-Hearer and Responsive.