My mind is always racing with ideas. I have ideas for picture books, middle grade stories, and young adult novels. And I have ideas for adult lit as well. Once I asked an industry professional what I should do if I want to write for more than one audience. His advice was that I should pick "my thing" and stick to it. The thing is, I don't know what "my thing" is yet because I'm an unpublished author without an agent. It's possible that I might think one market is "my thing," but it really isn't. Once I get published or represented in whatever market I fall into, then I suppose that could be "my thing." But for now, I'm not going to hold back from trying out different "things" in my writing.
When a writer gets a book published in a certain market, they start to get branded as a writer for that specific market. So while I understand and respect the opinion of the first industry professional I spoke to on this matter, I am relieved that other industry professionals I've spoken to have different opinions. Others have told me that if I want to write for kidlit and adults, for example, that's fine- there are many agents who represent authors who write for different markets.
There are actually a number of writers out there who have written books for both children and adults. Some of them started off writing for adults, and then they published something in kidlit. Or vice versa. Some of these versatile writers include Neil Gaiman, Judy Blume, Joyce Carol Oates, and Jennifer Solow. If anyone could think of any more writers who have written for both the kidlit and adult market, feel free to add to my list.
Update: Just saw an article on CNN about J.K. Rowling publishing her first adult novel.