All my kids are ready when the parents arrive. coat undone but dressed. If the parent is late, they simply sit in the hallway and read or play games. Makes it much easier as my time is SUPER tight between pickup and when I start my second business of teaching (theres thirty mins in between). Also means a quick pickup and go. also I wind down all the "fun stuff" before its time for pickup (I dont have TV on during the day so its easier).
I also establish a routine for pickup and tell the kids this is whats going to happen and warn them "your mom is to come in a few minutes lets start getting ready".