I've begun printing mine on 4 x 6 card stock. I am still creating new ones too. I am going to put them in alphabetical order and hole punch the top corner and just hold with a ring. My daughter is going to have the characters sign their card with clickable sharpie-like pens I bought today.
When we get home, I am going to laminate the cards. And my dad has made her a leather 4x6 photo album that says something like, "Cameron's 2006 Disney Memories" and it has been decorated with paintings(? i think it's paint, not sure how you do this on leather, he's the expert) of the Fab5.
We will put the autograph card on one side and a picture of her with the character on the other. A few of the cards are below. We don't have the album yet. It's for her birthday (she doesn't know about the book) which is about a week after we get back.
Here are pics of some of my cards.