Restroom trailer for October 2026 wedding: how to keep it warm at night?

We're planning our wedding for October 2026 in Charleston, SC, with about 140 guests. The reception will be under a tent on my parents' property, with a band, dinner, and an open bar. It'll run into the evening, and October nights here can get pretty cool. We're looking at a restroom trailer with flushing toilets and sinks to keep everyone comfortable, especially after dark when temperatures drop. The trailer will be placed on level grass near the tent, and a truck can access the spot for delivery and service. My main concern is keeping the restroom trailer warm enough for guests throughout the night. How do rental companies typically handle heating for evening events in cooler weather? Do they include heaters, or is that an extra cost? What should I ask about when booking?