Hi Bootsie,
Looks like you have a lot of friends and family, (I'm not surprised). I used to work at a Boy Scout camp. I managed the Kitchen, and what we did was look at the serving sizes for each food item we were preparing. It is printed on the back of all foods. (although I just looked at my turkey and it says "servings per container: Varied) But most food items will have the servings per container on them.
Most of all my advise it to have fun, and don't take it too seriously if you mess up a little.