Permissibility of dedicating as Waqf a piece of land to the deceased children

Q: My son and daughter died, may Allah be merciful to them, and I own a piece of land. Is it permissible for me to make a Waqf (endowment) on their behalf? I intend to build two houses on this piece of land. A house for each of them and the revenue of each house shall be spent on offering a sacrifice, Hajj, and good deeds on their behalf under the supervision of an authorized agent intending that the reward goes for them. I have also declared another house as Waqf and joined them with me. I need to divide the piece of land I have and build a house for my son and daughter to be a Waqf for them. It should be noted that the potential heirs oppose this and say it is not permissible for me to do so, as this is considered an impermissible gift. I need to have a written Fatwa in this regard. May Allah reward you best! If it is permissible for me to do so, will it be permissible for me to move to another land before I build the houses. I intend to build the houses in a better place so as to offer them for rent for the benefit of the deceased persons. It should be noted that I have already declared the piece of land as Waqf. I need the Fatwa of His Eminence Shaykh `Abdul-`Aziz ibn `Abdullah ibn Baz. May Allah grant him success in doing good!

A: If the reality is as mentioned, it is permissible to assign the mentioned land as Waqf for your son and daughter and spend its revenue on good deeds such as Hajj, sacrifice, and Sadaqah (voluntary charity) on their behalf so the reward will be for them. (Part No. 16; Page No. 117) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.