I recommend
Wings by Aprilynne Pike. The Sony version is $11.89 which is $.34 cents more than the hardcover on Amazon. But I guess it just depends how you prefer to read it and how soon you want it. :-)
I've only read half of it so far but I found it very similar to Twilight. The main character finds out she's a fairy instead of finding out her friend is a vampire, but it's still a fantasy romance written for kids and young adults. Even Stephenie Meyer endorsed the book by saying, "Aprilynne Pike's WINGS is a remarkable debut; the ingenuity of the mythology is matched only by the startling loveliness with which the story unfolds."
The book briefly made it onto the NYT Bestsellers list when it came out in May. I guess the down side is that there's only one book so far. Your kids would have to wait for the other books in the series as they come out.