Can we only use campground supplied water without activating the pump from the fresh water tank and thus preserve the antifreeze that is therein?
Yes. In your fresh water tank. Using the campground water hook up directly to your trailer (City water hook up) simply pressurizes your system from a different point and will have no effect on your fresh water pump. They are designed not to backfill or siphon from this pressure. And yes, It will push out the pink stuff from your water lines, if you have pumped it into them prior.
The city water pressure WILL, however, fill your water heater if you have drained that too. If you have done a full winterization, normally a bypass to the heater is installed. I am guessing from your description, you haven't done that.
This is generally NOT a big deal for such a short period of time if city water is available to continually fill the heater....but the thing you need to consider is that it is possible any park you stay in may have frozen water pipes in the sites as well. The park I am managing right now has this issue. You should not run your water heater unless your system is pressurized and there is water in the heater. Much damage can occur to the heater.
My suggestion is to remember your car camping days and bring jugs AND have some way to drain your grey water waste as soon as you create it. Use the campground facilities for bathroom and shower tasks. Make hot water on the stove, and if you have an air pot or large thermos, use that to store small qtys of hot water for instant hand washing etc.