I grew up around cereals, both sets of grandparents, worked in Battle Creek, my mother’s side for Post, and my dad’s for Kellogg’s.
Ever read The Road to Wellville, by T.C. Boyle? Wickedly funny. (I didn't see the movie, but I'd bet it wasn't nearly as good). Tells the story J.H. Kellogg and the methods employed at the Battle Creek Sanitarium. I'm sure your grandparents had some great stories.
Good Lord! how did they raise their children? It'd be like a Deepwater Baptist marrying a Serbian Orthodox...