Well there are different ways to express this, e.g., how much weight in pounds of chicken, but since
its a chicken dish and not a straight protein serving, presumably served from a chaffer of some sort.....
a full sized, 4.00: deep hotel pan, filled a bit down from the top, would have an apx capacity of 11qts,
which is a bit shy of 2 cups each for 25ppl--more than a normal serving size IME.
That rule of thumb should also be close for the potato salad and veggie, even allowing for a bit larger serving
for the non-meaters.
There's always a certain percentage of Vegetarians or non-carnivores for whatever reason--such is
why I usually provided a vegetarian dish for those guests, usually a cheesy pasta dish, or pasta/marinara etc.
And to contain the "everyone wants some of that too" phenomenon, I would always ask the client to have the
vegetarians be served first if possible, give them their fill, then put the stuff away (out of site) and serve the
remaining guests. This way the vegetarians never felt "punished" by not being included in a main dish, and the
other guests couldn't appropriate their dinner.