It’s not a bad idea to tidy up, make sure you have enough TP and post a sign on the bathroom door to identify it. You don’t want people wandering around your place in their time of need! If you want to be proactive and happen to have an available second bathroom, offering an alternative for the Performer/crew or during any extra busy times (i.e. between sets and right after the show) can help reduce waiting times and make your guests feel super special.
It is important to notify in your Venue description if your facilities are unique and/or anything beyond the expected - for instance if your venue has an outhouse or if your bathroom is not accessible, you may wish to mention that to avoid any surprises.