Say you are part of a 121 crew where either the CA or FO is down, what would you do in regards to px? Obviously announce you are returning to the airport, or landing elsewhere due to a medical emergency, but would you tell them the emergency involves one of the other pilots?
Secondly, in regards to that airplane mentioned above where a PP came up front to help out with the basics...How do you make that call? Do you make an announcement over the PA system asking if there is anyone on board with flight experience? Or do you have a steward/ess quietly go seat to seat asking? Either way, px are going to find out, and I think some will be very nervous.
I'd imagine that it all depends on how you make the announcement, ie- explaining this is the reason for two pilots, and the airplane is fully capable of completing a standard flight/landing with one pilot, however, thats a chitty situation...I'd be just as concerned about getting medical treatment to px in the back who'm may have a panic/heart attack, or any other medical emergency after hearing the news.