I am always surprised that old people are so frightened and timid. As an old myself, I feel the opposite. I will be dead soon, I want to grab as much in the way of interesting travel experience while I am still relatively fit and able to do it; the day that stops being possible is unknown and could be any moment. If my plane crashes -- well I am past 70; I have had my share and I can think of a dozen more awful ways to shuffle on. When it is American old people it is even more ludicrous since we live in a country where getting shot by some rando is a lot more likely -- in church, in school, in the shopping mall, at the theater -- than dying in a terrorist attack in Paris or anywhere else. When did we become the land of the frightened?
Re safe areas of Paris -- there really are not unsafe areas in Paris itself; crime is rarely violent, people don't carry guns, most crime is petty theft easily avoided by not being a walking buffet for pickpockets. What is often meant by safe is 'upscale' and 'white' -- in which case the list of arrondissements given is helpful. We have stayed in about half the arrondissements including the 19th and 20th and have never felt 'unsafe.' We have shopped in heavily ethnic areas of the 18th and never felt unsafe.