DH and I saw it. I can't imagine taking either of my children at 2 and 5. I would personally say 8 at the youngest. Pretty much everyone physically injures everyone in this film, there's death, blood, and dismemberment. I can't imagine a child that age really liking the messages in the movie and I think if they like the film, they're just getting the loud, motion, and anger and not really understanding some of the scary aspects--like that, purely out of momentary anger, one wild thing rips another one's wing entirely off and it will never grow back. That the wild things and Max throw rocks at people who say they do NOT want to participate in their game, and who are already injured, and who are facing the other way, not participating in their game, and draw blood and cause injury. That they've eaten many other kings who came to their world.
This is literally an adult film "edited for TV" and then repackaged as a family film to sell tickets. That's what Spike Jones intended it to be, wrote it to be, cast it to be, shot it to be, an adult's version of what childhood is about... but the studio made him reshoot several scenes because they wanted to market it as a "family film" (truly, this was done and edited 2 years ago, but couldn't be released as a family film). As an adult film, it's great, although it also makes me infinitely glad to have survived as a child of the 70s, glad not to be living in the 70s, and glad to be a female. I would call it "the brutality and beauty of being a boy growing up in the late 70s or early 80s."