Most people think that comic books are for kids. All comics are just super heroes in spandex that save the day and live happily ever after. That used to be true up until the 1960s, which makes me wonder how adults in their 30s and 40s still hold this to be true. In fact, mainstream comics haven't been for kids for a lot longer than that. Most of the industry has cycles of accommodating for younger readers, then maturing the same titles to match their readers. It certainly held true in the early '90s (unless I'm totally misinterpreting the child-friendly Spawn) and I more or less kept with comics until a year ago. Most mainstream comics are very "mature", not "adult" as you might infer. Sure, there are well-sculpted characters, over the top violence and language that isn't appropriate for schools, but extreme examples are usually labeled like music.

That said, there are plenty of comics available for kids. Major publishers liek Marvel and DC have realized that their revenue generating books are no longer for the kiddies and that if they want to get a new audience that will hopefully get into the more mature material, they gotta aim young. That's why they've actually create new sizes of books with more appropriate material that is perfect to get kids into reading and what we in the 'biz call "sequential art".

Marvel has what they call "Digest" sizes, which are smaller books, perfect for kids. Essentially, they're tiny versions of trade paperbacks, but they're unique material written for children.  DC has similar books pertaining to major characters and teen teams. As you can see with this example, the art isn't terrible, but it definitely doesn't have the sophistication of modern, mainstream comics. There aren't the more mature themes of sex, drugs and rock and roll, but they focus more on just fighting crime. The language is simplified, adapted for younger readers, meaning that these make great books to get kids to read since Goosebumps isn't what it used to be (in my day).

If you're a parent, I highly recommend taking a look at these at your local comic book store. Books are usually about $5-$10 a pop. I would definitely recommend Runaways from Marvel and The Batman from DC.