I would not mail toffee to FL this time of year, unless you send it overnight
I get stuff mailed this time of year and have learned my lesson. Anything with oil in it....has arrived with at least one or two containers popped open from pressure and made a real mess for me to clean up. Just recently, I received a load of Kitchen Basics chicken stock, with one package popped open, and boy were they hot. I am not a packing expert, but will take a chance on a suggestion: can you put ice packs into zip lock bags to protect the toffee, and put the toffee into a canister of some sort?
I know that this time of year if you order anything that melts, the shipping costs are outrageous. I always need to remember to order some items I get, in the winter or fall.