Is it permissible to pay Zakat on profits from the sale of a plot of land without the father's knowledge, especially if he is the owner of the money and a portion of the money is at the son's disposal, given that the son, mother, and siblings wish to hasten its payment while the father believes in delaying it due to the circumstances of the children's marriages?

It is not permissible to delay giving out zakat (definition) without a valid excuse, and what was mentioned is not an excuse that allows for delay. The father should be advised and reminded of the impermissibility of his action and warned of the inauspiciousness of disobedience. Giving out zakat from his money without his knowledge is not sufficient and does not relieve him of the obligation.