Restroom trailer generator vs shore power: which is better for winter?

I'm setting a six-stall restroom trailer for a three-day outdoor wedding in late November. The ground is flat and the truck access is good, but the forecast says it'll drop below freezing at night. The trailer has electric heat strips and an insulated underbelly, but I need to choose the power source. The venue offers a 50-amp shore power hookup about 100 feet away, or I can run my own 7000-watt generator. Shore power is quieter and won't need refueling, but a long extension cord run could cause voltage drop that affects the heaters. The generator is noisy and needs diesel every 8-10 hours, but it's right at the trailer. Which is more reliable for keeping the pipes from freezing: shore power or a dedicated generator? Does the cord length matter for heating elements?