When the campground rules says no engine idling I would take note. No campground I've been to has ever done so.Nor are there rules against a lot of all the other things people complain about. So if the campground doesn't complain I'm good as far as I'm concerned.
Just this last week we had a fiver pull into a KOA at exactly 12:33 am (when he woke everyone up), with a partially function muffler. He spent the next 45 minutes trying to get the trailer in the spot in the dark. Pulling forward,backing up,over and over.Then another hour making noise setting up. When he was done with that he left the park for a while and returned.It was past 2:00 am before we could get back to sleep.The next morning you knew who it was, as he was out their wrenching on it.
I made it through my trip without letting it eat away at me, stuff happens, my diesel idling for 5 - 10 minutes is nothing IMHO.