For me, the stories were entertaining. The best part of the book was Dumbledore's commentaries on the story. As a probably too discerning reader, I felt like Rowling was setting herself up for an unwinnable task. Writing fairy tales that set up the foundation for literature in the world is a weighty task. Trying to create a new version of Cinderella that has all the characteristics of good and evil, the moral at the end, and the enduring narrative that resonates with generations - that's no small feat. In that, I don't know that Rowling succeeded. The story I liked the best was the story that had originally appeared in the Harry Potter series. It seemed the most well conceived.
As for reading the stories to my kids: same thing. I know I'm overly protective of my boys and try to keep violence at bay, but I didn't find the stories compelling enough to keep their interest while simultaneously downplaying and ignoring the inherent violence in them. Don't get me wrong, every fairy tale has violence. But in Cinderella you don't focus on how the mother died - it's just a background plot point. The violence in the wizarding stories are a bit more up front.
All in all, not a bad book. There's a bit of me who feels like Rowling is just writing in the Harry Potter world because its easier and she can keep making money. But, I read the description of the foundation who this book supports and I laud her efforts to make a difference.