What could have been done for damage if a minivan was driven on the highway with radiator not working properly, and was overheating?

When my 03 cooling fan relay quit the temp would only get high during prolonged idling. I would drive it for less than 2 miles on the highway to cool it down. A smart mechanic will also open the windows and run the heaters on high to keep the engine cool until it can be repaired. Unless you have lost your coolant or your water pump isn't working and you allow your engine to overheat, no damage should be should be done.