With a cane or umbrella I would use the left hand and keep him back by jabing at him, giving me time to draw the pistol and put a double tap into his center of mass. That would be a legal repsonse in Florida to an attack with an deadly weapon. Retreat would not be possible because he has too many available hostages.
"As I looked at my two young sons, each with his gun, and considered how much the safety of the party depended on these little fellows, I felt grateful to you, dear husband, for having acquainted them in childhood with the use of firearms."
-- Elisabeth Robinson, in The Swiss Family Robinson by Johann Wyss