Off the top of my head, here are my top 6 recommendations for 3rd-5th grade level books that also have movie tie-ins. My kids read and enjoyed the books and also the movies for each of these:
The Sign of the Beaver
Charlie and the Chocolate Factory (If you watch the movie, the Gene Wilder version is much better, IMO, although the Johnny Depp version does follow the book more closely.)
The BFG
Shiloh
Charlotte's Web
Because of Winn Dixie
The Chronicles of Narnia are wonderful, but if you do one, you should do them ALL, and that's more than 6 books with that one series alone. :)
My Side of the Mountain and A Wrinkle in Time are also quite good, but they are 6th grade level, I think.
We also read The Indian in the Cupboard (also 6th grade level?), and started to watch the movie, but stopped it a few minutes in because we felt that the language was inappropriate for youngsters.
Mrs. Frisby and the Rats of NIMH (6th grade level) was a WONDERFUL book, but the movie (animated) was AWFUL. It added elements of magic/sorcery which were not found--or even hinted at--in the book.