It's not uncommon for non-rev passengers to take available jump seats as far as I'm aware, however, I thought there were legal restrictions on who is allowed to sit in them as they are close to the emergency exits and also have different seat belts which might be a hindrance in an evacuation. I suppose this isn't a problem for the retired captain as he would certainly be used to them but if his wife had never worked for an airline, I doubt she would be eligible.