Spending the remaining amount of the returns of the one third in charity

Q: According to the copy of the will attached to this letter, the testator (may Allah be merciful to him) divided his estate into three parts; two-thirds for the inheritors and one-third for himself after his death. As his share includes a business organization, shares in the electric company, a building, and some cash, according to the attached statement, he said that an Ud-hiyah (sacrificial animal offered by non-pilgrims) should be slaughtered for him from his one-third,and that Sadaqah (voluntary charity) should be distributed, and he determined the ways it should be done and who should do it. What he bequeathed does not exceed (Part No. 16; Page No. 410) 400,000 Riyals and the annual income from his third is around 4,000,000 Riyals. He mentioned in his will that his older sons, relatives, and friends should establish a body to discuss how the excess income from the building rent, proceeds from the heirs’ shares, the building included in his one-third share, and his joint-stock company, can be increased through transactions in which there is no trace of the Haram (prohibited) Riba (usury). This was the only reference to the income from his third.The inheritors include nine minors, and the Ministry of Commerce regulations prevent the registration of organizations or shares in the name of a deceased person. The inheritors therefore agreed to allocate a specific sum of money from the third every year for building maintenance, and then pay the money that the deceased ordered to be spent and add to that an almost equal sum which should be given away as Sadaqah. Another amount will be allocated as a reserve for the following year and the rest will be distributed to the heirs as their lawful inheritance. What is your opinion on our agreement; is it permissible? Please advise us and may Allah reward you with the best!The will also include the following statement: "I also bequeath that 100,000 Saudi Riyals and 50 Qatmah of rice (one Qatmah = 10 kg.) should be given every Ramadan as Sadaqah on behalf of me, my father, mother, grandmother, (Part No. 16; Page No. 411) their forefathers, my children, and my wives. They should be distributed among the poor, used to maintain Masjids (mosques), and spent on what benefits the dead. This should be done under the supervision of Shaykh ‘Abdullah ibn Sayf, his son ‘Abdul-Rahman after him, and then whomever he sees or the heirs see fit from the righteous. In addition to that, 30,000 Riyals should be given annually during Ramadan to relatives and needy friends, supervised by the heirs.10,000 Riyals should be given every Ramadan in the name of a benefactor to the Charitable Committees in Makkah Al-Mukarramah, Al-Madinah Al-Munawwarah, Riyadh, Dammam, and Buraydah. Each committee should receive 10,000 Riyals and so the total will be 50,000 Riyals. Five good Ud-hiyahs should be bought annually; one in my name, the second in the name of my father, ‘Abdul-‘Aziz ibn ‘Abdullah ibn ‘Uthman and his mother, the third in the name of my mother, Mawda bint ‘Aly Al-Dumar, and her parents, the fourth in the name of my grandmother Haya’ bint Talab and her parents, and the fifth in the name of my children, wives, and their parents. All these expenditures should be paid on time from my account in the Najd Commercial Corporation, under the supervision of its manager. I make my inheritors responsible before Allah for violating this will."