According to ESRB, this game contains: Mild Violence
Parents shouldnt be worried about Pikmin. If the child is old enough to figure out the controls, theyre old enough to handle the content of this game. There is some mild violence, as your army of carrots will have to battle numerous creatures and run the risk of being burned, drowned, bitten or trampled in the process of wandering around the levels. However, the violence is treated in fairly cartoon-like fashion, with no blood, although the fact that the little buggers are so endearing and make happy little squeaking sounds might affect sensitive younger children.
Any Nintendo fan/Miyamoto maniac has probably already picked this one up, but if you havent, you should definitely put it on your to-get list.
Deaf and hard of hearing gamers should be glad to know that all of the most important information put forth by the game is done via text.