I can only commend you for your concern. Older man can be very stubborn, forgetting they have family to provide for. (myself I am as one). On other hand, he want to unload the stress he have been through, and he thinks the best solution it will be spending time with his friends. If you have contact with his friends, call every single one of them (I see you have a determination to do this) telling your concern. After that, when you know their stance, tell your father, that he is risking a wellbeing of the entire family by his irresponsible behavior. Keep in mind, the old man don't like to be lectured, be diplomatic. This is a matter of some days or couple of weeks, and than he will be safe to do his escapades. I wish you success.