The movie that comes to mind for me is Matango. It’s a 1963 Japanese horror film by Ishirô Honda (the director of the Godzilla movies) that IMDb describes as “Shipwrecked survivors slowly transform into mushrooms.”.
I was curious what other PG horror movies people like. I find a lot of the time the limitations or target of an age rating can become noticeable and distracting.
Old Yeller. A proto-zombie story where a boy is forced to kill the friend who saved his life. A coming of age tale.