My kids get away with heaps more than I ever did as a kid, but they have still have fairly strict boundaries. Eg We had a family up the river last week with 5 children and they spoke to their mother terribly, didnt pack up ski gear etc. One of the boys aged nine called his mother a c--t and was a right little sh#t the whole week. If one of my children called my wife that they wouldnt walk for a week and forget about going skiing etc for 6 mths. The mother basically excused the behavior because when he gets tired he gets grumpy and not 5 minutes later he was skiing behind the boat.It certainly makes my wife and my self appreciate our children a bit more.
My favourite saying is: before you have fun the work needs to be done.