Hi Terry,
What a fun project! I am sure your son is having a great time reliving his Walt Disney World Resort Experience by making a Scrapbook for school. I am impressed that you made it all the way to the letter X - you must really know your Disney Facts!
Thinking of the letter X the first thing that came to my mind was X-Men; since Marvel is a part of Disney they "technically" are part of Disney. With that being said, the actual "rights" are owned by another company, however, the
Disney Store is selling X-Men DVD's so I say it is fair game. You could also choose XR - a character associated with Buzz Lightyear. Xyla was a toy Xylophone belonging to Alma who visited Doc McStuffins clinic on an episode of Doc McStuffins. My last selection could be a little far-fetched. Here in Canada, we have a television station named Disney XD. You could make a page based on the characters found on that channel.
The letter Z offers a few more well known choices. My favourite would be Zazu from the Lion King followed by Zeus in Hercules as well as Zorro. Some less popular characters are Zephyr from the Hunchback of Notre Dame II and Ziggy the Vulture from the Jungle Book.
I hope that helps Terry, I am sure your son's Disney Scrapbook will be absolutely magical!
Stephanie