Putting stickers on each page of the autograph book is exactly what I did, too! When my family first started looking for characters, my nephew Ben couldn't read yet, so I thought if each page had a sticker of that character, then Ben would know who wrote the autograph. If you put the stickers in before you go, it also helps you know which characters you already have, and which you still need (my Brer Fox page has been blank for over three years!). Like the above poster, I got most of my character pictures from cliparts on the Internet, then printed on my printer on sticker paper. Some very rare characters had no cliparts, so I had to scan the characters from old Disney story books.
If you want to put the stickers in before you go, I found the hardest part was trying to organize the autograph book - do you put the stickers in alphabetically or by movie?? Or by who is most common in what park?? Decisions, decisions!!