My husband is 6'4" and it's a pretty tight fit for him. The problem is that there is not a lot of leg room, especially if you have a child sitting next to you. They will let him ride by himself though, so if you only have one child that will make things easier.
You'll run into the same problem on Big Thunder and Space Mountain, although they are not quite as bad. And on Rock N Roller Coaster, try to sit in the front half of the car for more leg room.
Have fun!