Pemberley, two books that my ds loved when he was little were Journey to the Center of the Earth and Around the World in 80 Days. It's been ages but I remember loving The Black Stallion when I was in 2nd grade.... But that's so long ago I don't remember if there was anything really sad or scary in it. I also loved loved loved the Marguerite Henry books -they aren't incredibly long or complex but they were captivating for me as a young girl
A few books that aren't classics and aren't up at 10th grade level but your dd might also enjoy are The Warriors series and Hugo Cabret. I haven't read Wonderstruck yet but my ds loved it too.
polarbear
eta - I apologize that these aren't up at the 10th grade level, but when you're looking to fill this in, I also loved reading the Ladd series by Terhoune at around 2nd grade.
