I suppose the best way to avoid this happening in future might be to contact AA special services in advance of the flight to notify them so they can make any appropriate preparations, and to advise the flight crew discreetly at the beginning of the flight of your family's situation and that your father will be ordering for your brother as this setup works well for your family. If you had given them such a heads-up and an FA still got in your brother's face, I could see more of a cause for concern.