Hi Wendy!
My dad is almost six-and-a-half feet tall, so I understand the difficulties that come with traveling with tall people! That being said, the Walt Disney World Resort has very few rides that have maximum height restrictions! The only attractions that have a maximum height limit are
Tike's Peak at Disney's Blizzard Beach Water Park and the
Bay Slides and
Ketchakiddee Creek at Disney's Typhoon Lagoon Water Park. Although there are minimum height requirements for some of the more thrilling attractions, there are no rides that have specific maximum height limits in any of the four theme parks.
Generally, I have found that the biggest problem that he will encounter is knee room on some of the tighter-fitting rides. Although he will still fit into the vehicle, he may not be as comfortable as shorter guests. The front row has more legroom on many of the attractions, including those attractions that have boat ride vehicles. If this is a concern, he should be able to request to ride in the row that will be most comfortable for him.
Avatar Flight of Passage is the one attraction that may be a problem, but luckily, there is a test seat outside of the ride queue for him to try out before waiting in line! If your son-in-law has any concerns, he can always speak to a Cast Member before entering any of the attractions, and they will be able to help him make the decision that is right for him!
Have a Great Big Beautiful Tomorrow!
-Lindsey N.