I've decided to keep just their journals/writing books, the stories are too cute. Everything else is going!
We did the same - I kept one book per child per year, usually the one that had their free writing in it. By secondary school I just kept one or two essays per year and the odd piece of pottery.
They're pretty funny to look back on now!
I also have one of my dad's writing books, a couple of my mum's, my grandfather's and my great-grandfather's handwritten religious verse books. I love family history, and *someone* has to be the first to save this stuff!