Family of 5 on oxygen ain't going to make them happy. As a rule of thumb, Turbo is between nice and necessary, if you usually need to fly high and make use IFR reliability. Keep in mind the non-pressurized fuselage. A decent from FL250 with family on board may sometimes mean not steeper 500fpm ... a long way down and for the usual family trip usually a NoGo. My rule, if you are longer than 30 minutes on descent the advantage of the turbo is gone and down low you don't need it. If you typically have 2 hours trips, there may even be no difference for non-turbo vs. turbo, so I would abandon the expensive turbo idea if I were into a family aircraft.