You might just decide to make his day by turning yourself into (wrapping paper roll) "SwordMan."
You will probably try to capture the moment on your handy iphone--totally blurry--but it captures the essence of the moment. :)
And you might strike menacing poses and say the only fencing lingo you know, "on guard," easily one hundred times. You might even leap off of the couch in mad pursuit because after all they seem to get the biggest kick out of that themselves and maybe you would want to see what all of that leaping hype is about.
Trying to escape in their "boats."
And then because you're out of breath from all of that "rough-housing" you might just have to take the battle to finger-fencing in the raspberry bowl.