Is it permissible for a married woman to pay for her indebted husband's 'Umrah expenses and for her son's, as a gift from them, so that they may go for 'Umrah?

It is not a condition that the expenses for Hajj or Umrah come from the pilgrim's own money. It is permissible for a wife to give her husband money for him to perform Umrah with her. As for the travel of a indebted husband, if the debt is due and he is able to pay it, he must settle it before traveling. Otherwise, he is not permitted to travel except with the permission of his creditors. However, if the debt is deferred, or if it is due but he is unable to pay it, then he may travel even without their permission.