At 2 my son was scared of the characters and wouldnt go near them without me. DD was also scared of them at 15 mos and buried herself in my shoulder (and still does if anyone acknowledges her).
However, I still got an autograph book for DS on his first trip (now the kids share one as I only need one signature). Now he is 5 and Im so glad I did it. Heres what I did-I took pics of him (sometimes he and I) getting the characters autograph on every trip. I scanned the autographs into the computer, shrunk them down and then added the pics I took to each character to make a 4x6 page. I got a photo album in the park and put the pages in it. He loves to look at his pics over the years, how much he has grown (and how brave hes gotten), etc. DD loves to look at hers and her big brothers too. I dont change the pics as the years go by, but you could. If you got a big enough book you could put all the pics in there.
alison