The idea of 4 duplicate books was too much for the last WDW trip--this is what we did:
DD,13 carried the stuffed Pluto dog made of canvas fabric. The leash could be snapped so it could be worn like a shoulder bag so it was easy to keep up with during the trip. Of course Pluto made a huge fuss over her when she asked for his autograph--and she enjoyed that more than she would ever admit.
When we returned home I embroidered over each of the autographs with colored floss to "match" the characters, i.e. black for Mickey, red for Minnie, orange and black for Tigger, light blue for Cinderella, royal blue for Snow White, purple for Goofy, etc.
Pluto has resided on her bed ever since and her friends always comment on it.
DS, 5 used an autograph book we made. I bought a Mickey 4X6 loose leaf style photo album at Wal-mart. I took out the pages and sheet protectors to use when we returned home. We used coloring books and downloaded images from the internet to accumulate as many different characters as possible. Then I enlarged/reduced them as necessary and copied them on cardstock paper. I punched holes and reinforced them with the little circles. DS and DD passed the time on the drive down coloring the pictures with markers. CMs always made a big "to-do" when they were asked to autograph their own pictures.
When we returned home I reassembled the album with the character picture/autograph on one side and his picture with the character on the other. He still enjoys looking at this on a regular basis and we will be taking it back with us next spring.
HINT: Be sure to get the jumbo Sharpie--you can tie this to a color cord for the child to wear necklace style so you aren't always fumbling for it. The jumbo size makes it easy for the character to grip and sign.
DN(Disney nephew), 10 was too "cool" for an autograph book so he wore a light colored Disney shirt and had the characters sign it with the Sharpie.
Other DN, 12 opted to wear a hat and collect signatures.
Hope these ideas help!!