Neil Gaiman once made a comment on his blog about passing stories on to his children. I don't remember exactly what he said, as though I took the time to write it down once upon a time, it got subsequently lost in an internet shuffle with another project I was working on (I blame Yahoo). The essence of it boiled down to the importance of sharing stories with your children, and how it's not only good for them but for yourself as well. It wasn't just about parental bonding, either, but the importance in and of themselves of stories and their telling.
I was reminded of that recently when I started reading The Wizard of OZ to my little girl. We have been reading books for years, but she's recently started to move from the standard picture books into more complex picture books. I've had OZ on my shelf for years, along with Alice and Pooh, since before I had or had even considered children. With regards to Alice and Pook, they were stories I enjoyed, and as for OZ, it was bought with the notion that maybe someday I'd have someone to read it to.
While Dorothy will never replace Alice, or Pooh, for that matter, I did enjoy the story. I was also surprised from the start to discover that the change from a black and white world to one of technicolor was not something done just for the movie. For those who haven't read the book, I don't think I'm giving anything away by saying Kansas is written by Baum to be literally grey. Everything he describes in Kansas is said to be dull and grey, so that the colors explode when Dorothy arrives in Oz.
(Not literally explode, mind you, at least not until Michael Bay does the remake.)
I don't plan on ever writing for children - though there is one idea clanking around in my head - but I think the sense of fun that is imbued by most children's stories is a good thing to interweave into any story, no matter the audience. Even if you're writing horror and want to scare the socks off of your readers, they should still have fun even as they're losing their footware. I also think it's probably not something that comes with trying to do it. Like humor, it will likely lose a lot if you try and actively make your story fun.
Just as importantly, there is a sense of discovery that seems to come from these books. Baum and the others have a real gift for crafting worlds where each corner turned brings something new. In an adult work it would be too much, and I noticed there were inconsistencies and things that just didn't make sense (in Through the Looking Glass it can be hard to follow the geography of Alice's travels, and there is supposed to be one, for example). But it was still nice to see an entire world where, unlike in a lot of modern works, the author made it up as they went along. Nowadays "world building" is it's own thing, and maybe Baum and Caroll could teach a thing or two about that.
Almost every writer I have ever read who commented on what it takes to be a writer has stressed that they read. A lot, and all kinds. It wouldn't hurt to put a few children's books on that list, even if they are things you read once as a child. Take it from me, they take on new life reading them as an adult.