I turned on "Chitty Chitty Bang Bang" for my kids, and I was interested to see the book was by Ian Fleming (I already knew this)--the same guy who wrote all the James Bond novels--and the film was produced by Albert Broccoli (same guy who produced the original James Bond movies).
But here was the great joy--the film script was written by Roald Dahl!
That explains the whimsy, the portrayal of both the kids and the adults, the dressing up as dolls, etc.
Now that I think about it, Dick van Dyke and Roald Dahl are a rather excellent combination, aren't they!
And yes, the movie is rather long and tedious (Dahl was a novelist, remember), but my kids are entranced. He got all the right elements in there!