According to ESRB, this game contains: Mild Language, Violence
Parents should have no trouble with picking this game up for their children. Sure it's violent, but the violence is relatively clean and harmless, and all the death inherent in swinging sharp implements about willy-nilly is completely glossed-over.
Parents in the UK: now that mentioning ninjas is legal in the British Isles, the former TMHT are once again an appropriate gift for your children.
Deaf and Hard of Hearing gamers, there isn't any linguistic information other than the text mission briefings. You may miss out on the colour text from all the characters, but it's not vital to enjoying the game.