I have the encyclopedia, but it is heavy so I didn't want to carry it around the parks. I decided to bring a matte for a photo - and then promptly forgot it in the stroller.
Luckily, for our Tusker House breakfast, I had brought my son's pith helmet that we got for $5 from our local zoo. When I realized I forgot the photo matte, but remembered the marker, I had the characters sign his pith helmet. He LOVED it. I was so glad I forgot that matte because he still loves pointing out the signatures on his hat that he can wear.
The characters also really loved that he had a hat similar to what several of them were wearing. They made over him quite a bit for it.