Figurine pulled pork, you will loose 40 to 50 percent of the uncooked weight during smokin. Then figure on a 1/4 pound of meat for each sammie, men will eat two sammies, women most likely one. Take the 1/4 pound figure times the number of men you think you will be servin, then take the 1/4 pound figure times the number of women you think will attend add these two together and then an additional 10 percent.
Now sides are a bit tougher, The best way to decide how much you need is to make some up. Say tater salad as an example, take a pound of taters and make up a batch. Scoop out into servings and see how many servings that one pound of tater salad will feed. Same for any other sides.
Food is only a small part of a caterin business. There is equipment, insurance and health department rules to consider. I am in the process of fact finding for the same. There are so many things to consider. Good luck hope it helps.