Vacation
In 1979 John Hughes wrote this story for National Lampoon. It’s called “Vacation ’58.” Most of it will be extremely familiar.
http://www.bizbag.com/Vacation/Vacation%2058.htm
Warner Brothers bought the story from the Lampoon and hired him to turn it into a screenplay, and if I read right, that was his first job in Hollywood.
All these years, I didn’t even know he wrote it.
One small warning to the reader: the story, unlike the movie, actually describes what happens to the dog.