I just found this great post by Sarah Webb on how many words a book should be. She, in turn, got some great info from kidlit.com. The general breakdown is as follows:

• Board Book — 100 words max
• Early Picturebook — 500 words max
• Picturebook — 1,000 words max (Seriously. Max.)
• Nonfiction Picturebook — 2,000 words max
• Early Reader — This varies widely, depending on grade level. I’d say 3,500 words is an absolute max.
• Chapterbook — 10,000 words max
• Middle Grade — 35,000 words max for contemporary, mystery, humor, 45,000 max for fantasy/sci-fi, adventure and historical
• YA — 70,000 words max for contemporary, humor, mystery, historical, romance, etc. 90,000 words max for fantasy, sci-fi, paranormal, etc.

You can also check out Chuck Sambuchino’s Word Count for Novels and Children’s Books: The Definitive Post

Looks like I’m closer to my target word count than I thought I was. Guess that means there will be some serious editing in the near future.