I am an elderly woman. My husband and I spent ten years in Saudi Arabia for the education of our two older children, and I paid a large amount for them. However, I have a son and a daughter who are younger. I know that gifts in this world should be equal among children. Now, I have no money left, as all our efforts were for them. Of course, they want to get married now and will not be able to help their siblings with their studies. I own a house and a piece of land. Is it permissible for me to state in my will that after my husband and I pass away, the land and the house should go to the son and daughter, in the spirit of equal distribution of gifts, of course, in proportion to what I gave to their older siblings, but on the condition that they cannot dispose of them until after our death? Is this permissible according to Sharia?