There is violence but it's very very tame.
The movie is about 3 teen/pre-teen boys who know martial arts fighting with adults, many of whom know martial arts as well.
3 young boys witness an attack on their grandfather.
A babysitter is thrown into a closet with an entire pizza on her face.
Kidnappers try to kidnap 3 boys but the boys defend themselves in a Home Alone like style, except kind of more violent like including throwing CDs at them and drugging them with laxative cola. We see the kidnappers run to the bathroom and then as they prepare to come out, the boys in one scene are grossed out by the smell.
Tons of ninja fighting. A few scenes result in close calls of boys getting it. Very little if any blood
Also a young boy picks a scab on his arm.
A villain is shot.
5 ninjas come to attack an old man but 3 boys help defend him.