A good book for kids is likely to stay in print a lot longer than a book for adults. That’s why you need to be careful not to parody something kids won’t be familiar with, or to make cultural references that are going to go right over their heads a few years down the road. Something that happened ten years ago or when you were a kid may be completely unknown to kids today. That goes for cartoon characters, popular movies or bands, famous actors, etc. And even if you do reference things that are cool right now, will they be tomorrow? Or will they date your book, making it less likely to appeal to tomorrow’s readers?