I've ordered illustration board for the hard covers via Hobby Lobby online. In the meantime, I'm spending time in Photoshopland creating the print-ready files for the book pages.
I've made all the images the correct dimensions and resolution for printing, and am dropping them into the layout template. Here is what one of the print-ready files looks like. (above) The top rectangle is where holes will be punched, and the book will be bound.
What's next: I will look for papers for the book pages and covers.