Is it considered a breach of an oath if a person swears not to take a sum of money, and then his son takes the aforementioned sum from him, and not he himself?

The summary of the answer: Breaking the oath here depends on the intention of the one who swore it. If his intention by the oath was that he himself would not take anything from the patient, then he does not break his oath if his son takes the money. However, if he intended that neither he nor his son would benefit from the money, then he has broken his oath and must offer expiation. This is because an oath is based on the intention of the one who swore it, and generalizing the intention for a specific wording is considered valid according to the preponderant opinion.