Taking the advice of my fellow and sister hounds, we did not go to the Plaza but instead chose the Astor Court in the St. Regis (this over the Pierre because the Astor Court has a harpist). Wonderful. A room so quiet that it is easy to imagine that you are in NYC 100 years ago. In the next room is a Maxfield Parrish mural; in the Astor Court, all sorts of mythological murals. Much more intimate than the Palm Court. Exquisite table settings, needless to say.
As for the goodies, there was a huge selection of loose teas (we had the Astor Court blend of Early Grey and ginger); tender scones served with yummy lemon curd, clotted cream, and jams; a nice selection of tea sandwiches; and lovely petits fours. Best of all, the waiter returned regularly to replenish our three-tier tray with new scones and sandwiches. Needless to say, this was our dinner. ;-) Actually, every time we ate a few scones he appeared with a new plate of them. It was getting comical. Finally, we decided to leave one scone and one sandwich on the plate so that he would not return. He did, however, come and add hot water to our tea leaves; this kept the tea hot and prevented it from getting too strong. I don't mean to make him sound obtrusive; far from it -- he could not have been more gracious. When you are comparing different afternoon teas in Manhattan, keep in mind that at the St. Regis you are getting an endless supply of goodies.
Over all, we felt utterly pampered by the time we left. Highly recommend. Will try the Pierre next year, since we've decided to make this a tradition. ;-) Thanks again for all your advice. Daughter is all ready for college now!