Last year it got right cold down into central Florida. OP, I probably wouldn't worry too much about it. Chances are that you will have a good amount of liquid in the tanks, so it will take some time to freeze... probably a day or 2 with it being way below freezing. You can buy the add on electric pads for your current one if you feel strongly about it.
Something I might research is the effects of pouring automotive grade antifreeze into your tanks. The RV stuff doesn't prevent freezing, it just doesn't expand until much colder temps. Automotive grade antifreeze actually lowers the point that the liquids freeze. If you poured a gallon of antifreeze into your black and gray tanks, that would probably be sufficient to lower the point at which that liquid freezes. The only potential problem would be environmental concerns when you dump that antifreeze. I don't know how safe it is for the environment or sewage systems...
2015 Ram CTD
2015 Jayco 29QBS