I think celebrities should leave the children's books to children's books authors. If you're an adult, and you're not illiterate, write an adult book. Why are people like Jenna Bush, Ray Romano, Sting, Billy Joel, Jason Alexander, Lynn Cheney and Madonna writing children's books? Well, Lynne Cheney is probably about propaganda but for the others, it's clearly for publicity and to show "look, I care about children and kids."
Because children don't really need your books, guys. It's not like there's a massive hole to be filled in the market of children's books. There's a guy named Dr. Suess who wrote like a million books, so parents are pretty set when it comes to children's reading. I really can't picture many baby showers where mothers are going "oh, could you get me Jason Alexander/Sting/Ray Romano/Madonna's latest children's book, that's what everyone in town is reading, I really need a copy of it, I heard it was so great!" And trust me, parents don't want to introduce their kids to Madonna at age 4.
They don't want to learn about what you have to say because they're just kids and not into the celebrity culture. They're too young to relate to your marriage problems or difficulty for caring for elderly parents so chances are kids don't care about what you have to say, Ray Romano and they don't watch Sienfeld so ditto for you too, Jason Alexander