To be a true ninja, it's paramount that nobody
knows you're a ninja. Hence, this kid's father is
not a ninja, unless this is some kind of elaborate double-bluff going on.

Ninjas were not super soldiers who wielded all sorts of special weapons like nunchucks or katanas. They were spies, undercover agents, and assassins; carrying such flashy, expensive, and often prohibited weaponry was a good way to draw attention to yourself. Nor did they dress in black, which was just a convention derived from Japanese theatre. More than anything, ninjas would be dressed as some nobody or other, a servant, or a common citizen. If they had to kill someone, a simple knife or application of poison would often suffice.