Any gas powered generator used indoors can kill your entire family in a matter of minutes. In any event most of the small back-up generators out there are mostly a PITA to maintain and keep running for any length of time. Long term fuel storage is difficult at best and dangerous at that.
A good transfer switch, hard wired by a licensed electrician can be expensive, as is a quality generator capable of allowing you and your family not only to survive, but to live in relative comfort for weeks in any SHTF situation. A friend's Mother and Dad living in St. Louis were without electricity for 3 weeks just a couple of months ago.
There is a solution, it may look expensive, but what is your family's health and safety worth? Anyway, I opted to buy a propane powered 16KW Generac unit and connected it to my 500 gal. propane tank. It ain't perfect but it gives me (well) water and HVAC and can run for weeks.