Is the money that the father took as a down payment for the purchase of land, then refused to reclaim it when he learned that the land had been sold to someone else, and which his children spent after his death on purchasing a sacrifice for a wedding, lawful money, knowing that one شيخ (scholar) issued a fatwa (religious edict) that it is the children's sustenance, while another issued a fatwa that it must be given in charity?

The money given by the cousin is part of the father's inheritance, and it is not permissible to give it to some heirs without others unless they agree to it. If they do not agree to waive it for one of the heirs, it must be divided Islamically according to each heir's share. If all heirs waive the money to contribute it to their brother's wedding, then the action is valid; otherwise, everyone entitled to a share must be given their right.