The situation is, of course, complicated. Walt Disney World’s policy is that all people over the age of two must wear a mask inside the park. While the child in question apparently has some difficulty wearing a mask, and may potentially have difficulty understanding the situation, that’s not sufficient for an exception to the policy. There really aren’t any exceptions to the Walt Disney World policy. If you’re over 2-years-old and can’t wear a mask for whatever reason, the only available option is not to go to Walt Disney World.