I had the most rude 3 y.o. girl at my daycare for 6 months. She was soooo rude to her parents at arrival and departure. During the day with me, it was 85% attitude. I tried some advice I got, telling her to give daddy a big hug when he gets here and the first time it worked, but she was still being silly and not listening. I told myself hey its a first try. Well I didnt get many other tries, the next morning, tried to ''intervene'' when mom dropped her in as she was being so rude with her mother. The little brat started crying, it turned into a argument with the mother and me and how I was just trying something new and positive, result : mom gave me her notice on the spot !!!
Now I just let them do their thing and I keep on doing my things to get ready to close. But lucky me, my entrance and kitchen have a little door that separate the space and also my kitchen to playroom. So once parents get here, they wait in the entrance, I bring the child (or they walk to them) and then I close the door. Sometimes the kids want hugs and I say ''Only when you finish getting dressed'' :P