Really good book!
This is my favorite Harry Potter book. There are positive messages, interesting characters, and a clean, family friendly story. The mystery is intriguing and it's enough to encourage children to read. One thing you may want to discuss with them is rule breaking. Harry, Ron, and Hermione break a lot of rules. Even though the outcome is good, children should be told when it is and is not appropriate to break certain rules. Other than that, go for it. I would recommend that the American readers get the book on tape. Jim Dale is the best narrator I've ever heard and you and your children will likely enjoy each of his voices for the different characters.