The best cut for pulled pork is shoulder, usually called Boston Butt ( no idea where the name came from lol) and Picnic Roast... Any fatty pork roast is good because its the connective tissue and fat that melts and makes it soooooo yummy
You'd probably need at least 3 roasts, about 4lb each for that many people... I figure about 4 oz of meat per sandwich, which would be about 10 lbs, but you'd want a little leeway
I would season the pork with some salt and pepper, maybe some Cayenne if your the spicy type.
Slice up some onion, put some at the bottom of your crock pot. Put the pork in, then some more onion and fill it with water to cover. Then cook it for like 10 hours. Take it out, cool it ona rack over a pan.
To pull it, use a couple of forks and just pretty much take out your aggression on it. Then mix with your BBQ sauce of choice.
Basically, season it and you just braise the heck out of it lol!