Hi Nicole,
You'll be happy to know that there are companion restrooms located in all four of the theme parks, both water parks and the ESPN Wide World of Sports. You can see a list of the locations on-line by visiting the section for guests with disabilities - click
here. Scroll down to the link for
Restrooms for Guests with Disabilities at Walt Disney World to see a list of the companion assisted restrooms. Having traveled with my kids a lot, I've learned that it is important to scout out the restrooms locations ahead of time. Make sure you plan ahead as there is usually only one companion restroom at the locations and it can take awhile to get in on crowded days.
Be sure to visit Guest Relations to obtain a Guest Assistance Card for your father. This will help alert Cast Members that he may need special assistance at some attractions. Keep in mind that some attractions require guests to transfer out of wheelchairs in order to board the attraction and Cast Members are not allowed to lift guests on or off attractions.
Please let us know if you have further questions. Disney is a super place for guests with special needs. Here's wishing you magical memories!