Here is the best piece of advise you'll get, start smoking now!
Oddly enough pulled pork is without a doubt the best meat you can reheat, I really think like soup, stew & beans its better the second day. Smoke the butts ahead of time, pull and put in ziplocks in the reefer. Then the day when needed either heat in a crock pot, steam table, of an alum pan sealed with tin foil, all three will heat without too badly affecting the moisture content.
Moisture content! If you cook ahead it gives you a chance to help the moisture while at the same time adding flavor. There are a few recipes around here for "Finishing sauce" Personally I like Chef JJ's, you use just a wee bit for moisture and it also has all these delightful spices also. You don't really taste the spices unless you over indulge with the sauce, but it makes your pulled pork taste better than other's and no one can put a reason on it, Poof you are a smoking genius! reheat for the part, add a squirt bottle or bowl of warmed BBQ sauce next to the meat and a pan of warmed buns and you'll be a hero.
Smoke a head, a little at a time or all at once, but smoke ahead and don't be sitting around the smoker when its time to eat looking for the number for pizza doodle in the phone book. Seriously pulled pork is better tomorrow, you can smoke without stress, and allow longer sitting times for those juices to redistribute. Plus a chance for a bit of finishing sauce.
Smoke ahead of time and you'll be a happier person at the party.
80 people = 1/3 lb each 80/3 = 28 lbs. x2 for weight lost due to rendering = 56 lbs of precooked pork. I would smoke butts or shoulders, whatever you can get and get cheapest. Even at 1/4 lb servings you are still looking a 40 lbs. of meat with sides.