I can’t really recommend any of the new Disney-canon books since I’ve haven’t read any of them, but The Han Solo Adventures are some pretty fun and neutral SW books that should fit into the new canon without any problems. They are essentially about Han Solo’s “adventures” with Chewbacca prior to the events of the movies.
There’s also The Lando Calrissian Adventures books in the same style, I haven’t actually ready any of them, but they seem to be in the same over-all style, pre-movie Lando stories; depicting his adventures as captain of the Millennium Falcon before he lost it to Han.

Shadows of the Empire (which tells the story of what happened to Luke and the rest of the ‘gang’ between The Empire Strikes Back and Return of the Jedi) is also a book that shouldn’t contradict the new movies in any way. However, I’m not too sure if I’d recommend that to someone as young as 8. There’s nothing shocking in it, but the story might be a bit too complex, and one of the villains can definitely be a bit of a creep some times (I haven’t read it in a while so I can’t remember how specific the book gets. It’s probably not much though being a SW book). However, I’d definitely recommend that it to anyone that’s roughly 11-12 or older.