It does seem to me that about once a trip (I've bought the CD 8 times) one of the special photos fails (we're all pointing at the manhole cover, but nothing is there; we've got our arms in the cuddle position, but no Simba). Still, it's pretty impressive that they seem to work 80% of the time or so.
I don't know how familiar you are with Photopass, but you can also add borders and edit the photos (ex. crop them) and those enhanced photos will also be on the CD. You can also use a coupon code (I usually get them from retailmenot.com) when you check out the final CD (I've never gotten one to work during the pre-order. The code usually gets me free shipping of the physical CD and a big discount on a set of stickers or a magnet.
Have a great trip.