Restroom trailer for November 2026 wedding: how to prevent freezing?

I'm renting a 4-stall restroom trailer for my daughter's wedding on November 12, 2026. The forecast shows evening temperatures dropping below freezing. The trailer will be placed on level grass near the reception tent, about 50 feet from the nearest power source. We'll have 120 guests over 6 hours with dinner and an open bar. My main concern is keeping the toilets and sinks from freezing up during the event. What steps should I take with the rental company to winterize the unit? Do I need to ask for a specific type of antifreeze in the holding tanks or additional heating elements? How do I ensure the fresh water supply doesn't freeze in the lines?