In recent years, there's been too much emphasis on making the vocabulary and humor as child-like as possible. Nothing wrong with this for the majority of books.
But picture books can work on two levels--one for the child and one for the adult reading it. Moreover, there are all kinds of children in the world and some of them like sophisticated humor, even if they don't quite understand it. Personally, I used to love reading the cartoons in the New Yorker. It was a window into the world of adults, even though I didn't always "get" them.
CINDER EDNA has some pretty sophisticated one liners. Hopefully there's also enough child-centered humor to make it work overall. Seems to be--it's sold really well. Adults DO buy pbs, and it's also true that children like books better if they see their parent having a good time reading it.