If you’re getting Charlie and the Chocolate Factory, also get Charlie and the Great Glass Elevator by the same author. It has never been made into a movie, but it’s equally interesting.
Little girls and people who used to be little girls seem to love Anne of Green Gables. There are a couple of old films, but the definitive adaptation seems to be a 1985 CBC Television version.
As a boy I enjoyed reading and rereading Tom Sawyer. Huckleberry Finn is a more literary work that skews a little older, and it’s nice (but not strictly necessary) to have read TS as background. (It’s not entirely unlike the relationship between The Hobbit and The Lord of the Rings, come to think of it.) There have been many films of Tom and Huck’s adventures.
Hey, how about The Hobbit? Made into a flawed animated TV version back in the '80s, soon to be a live-action extravaganza produced by Peter Jackson.
Actually, *my * favorite book was The Adventures of Hajji Baba of Ispahan, which was adapted into a rather ill-regarded film. I’m not sure either the book or movie are strictly suitable for children.