There's a good round-up of writers talking about writing for children at The Guardian this week. (I see that Steph popped in ahead of me already - I hope this means we can look forward to a children's book from her soon.)
I was discouraged, I must say, by the following comment from the article by Meg Rosoff and Linda Newberry:
"Don't be misled into thinking that picture books must be easy to write because there are so few words."
That's exactly why I write them.