Last summer I bought Disney autograph books at the Emporium (sp?) on Main Street in Magic Kingdom ... they were cute but the paper was very thin.
This year I'm buying 6x6 cheapie scrapbooks from Michaels ... will have the character sign on the front side of each page ... then when I get home I'm going to use a couple of 5x7 Razzy Red (Creative Memories) albums and CM's Magic of Disney snap pack to make photo-autograph albums. I'll use the MoD snap pack to decorate the pages in the CM album, remove the signatures from the "cheapie" albums, mat the photos with PMP (photo mounting pape) and mount them on a page in the 5x7, put a photo of the character and child on the facing page.
CM doesn't make 5x7 albums any more, but the 7x7 Ltd. Ed. Strazz album would be perfect ... it's a pretty blue with a exploding stars design on the front and the pages are bright blue with red jeeping) ... the pages are so cute that you don't need to do any additional decoration if you don't want too. I'd be using these, but I already have the Razzy Red ones (which are also cute).
Or you can just bring a CM album ... get the characters to sign the pages on both sides of the pages, then when you get home insert additional pages between the characters, decorate them with the MoD snap pack, add the photos, maybe journal a bit and voila you have a wonder memorial keepsake album.
The 7x7 albums come with 12 pages and you can insert a page refill pack for a total of 48 sides.
I would definitely get two autograph books ... collecting autographs and making "smooshed" (i.e. pressed) pennies were my grandkids (5½ and 7 years old) favorite things to do last summer!