You can create a restroom break kit for each person you are traveling with, which could include: bars of soap, paper towels (never use the air hand dryers in restrooms), travel-size packs of toilet seat covers, and hand sanitizer. You may also want to get some disposable rubber gloves if you can find them. You do not want to touch any of the public bathroom surfaces, regardless of any virus, as they can be full of bad bacteria as well.
Stop at gas stations or highway rest stops and plan your trip ahead of time to know where you could possibly stop in case you need to go to the bathroom.
Overreacting? Possibly. But in if you are high risk for any virus and travel is still high on your list of things to do, you can never be too prepared. To find the nearest rest areas on U.S. interstate highways, check out this great website, InterstateRestAreas.com