As one of the authors, I can't help but recommend Rising Stars Early Years Mathematics. It includes parent posters and letters home as well as maths sessions and maths in other curriculum areas. Download free samples:
There are plenty of others out there, though, so do explore to find something that suits your situation.
I'm also a fan of maths from stories - there are so many story books you can build understanding with, and they can be cross-curricula too!