I definitely depends on the parent's attitudes and how into Disney their kids are. When my DS was almost 3 we went. He LOVED it and didn't stop talking about it. He definitely showed more excitement about his trip then some of his playmates who went at the same age. He wasn't afraid of characters and had watched the planning video so many times that he knew what everything was. He was so starry-eyed at Playhouse Disney in MGM and seeing certain charaters like Buzz and Woody. My DD was 11 months old and she was a happy camper the whole trip. Granted, she slept alot and will not have memories of it... but it was still a wonderful family experience. We are going this August when my DD will be 2. I think she might be fearful of the characters unlike my son... but as a parent I know that and have no expectations to "force" her to take pictures of them. The same goes with rides. If your kids are afraid they shouldn't be forced just because you may have enjoyed the same ride as a kid.
Parents should realize it is a family trip and if they put their kids best interests first it should be a wonderful experience for all.
Parents should realize it is a family trip and if they put their kids best interests first it should be a wonderful experience for all.