Make sure you take into account any special circumstances. The secret of satisfied diners is portion control. If you do not control the amount of food each person receives then perhaps the last people in line may not get any food. If you do not plan ahead concerning the portion size, then you might end up with expensive leftovers. Believe me, the person paying the bill for the meal does not want to pay any more than is needed.
Commercial establishments use scoops to control the amount of food each customer receives.
They do not use them just because they make pretty mounds of mashed potatoes. Some scoops are numbered according to the number of scoops per quart they yield. Other companies use different numbers. Be sure you know what your are getting when you buy your scoops. Below is a chart of approximate yields of scoops that you might find useful.