I'm certainly not a professional chef and am not supposed to post here but I have alot of experience cooking and serving pulled pork and other smoked foods for groups of 4 to 200 (this is my forte and I just do it for fun). Here is my 2 cents for you to take as you see fit.
This is my normal plan of attack.
The typical pulled pork sandwich serving is 1/4lb (pre-cooked) per person if you are serving sides and can go up to 1/2lb if you are lite on sides (read chips only). I always buy from Sams as I don't have a license and it's the cheapest here in Atl and the quality is pretty good. Buy in cases to get a discount per lb and get them with the bone in. I make my own rub and prep the bbq at least 8 hours before I decide to cook it. Buy some nice heavy coolers to keep the prepped meat in with sealed bags of ice unless you have a fridge big enough to hold 5 to 6 boston butts. Unless you have a smoker that can cook this much meat in cook it in the oven. I'm a "low and slow" guy so I would cook that much meat for about 10 to 14 hours but ultimately to at least 195 degrees and no more than 205. If you cook it to 195 to 205 and you cooked it slow (250 oven temp) it will fall apart with very little effort. A good rule of thumb is if the bone wiggles and starts to slide out easily it's done! If you have to cook it faster don't cook it to 205 or it will be dry.
When the pork is to temp keep it whole and wrap it in foil and either drop the oven temp to it's lowest setting until you are ready to serve or store in a thick cooler with blankets or anything to keep the heat in. Make sure the cooler is just big enough to hold all of the meat or the heat will disapate too quickly. I have kept whole butts for hours this way and they stay hot enough that you will need gloves to pull them. Speaking of which go buy you some nice thick chemical gloves (the kind you use when handling strong kitchen chemicals). You will need them when handling 200 degree meat with your hands. Machines and utensils have their place but that place is not pulling pork. =) Plus by hand you can remove the fat easier. Cooked properly you can pull 5 or 6 butts in 10 to 20 minutes.
For serving chafing dishes work well but make sure you have some liquid in the pulled pork to keep it from overcooking and drying out. A good vinegar sauce is perfect for this and the flavor it adds throws it over the top.
I can give you a good recipe for the rub and vinegar sauce if you want...just email me at email@example.com
Sorry again for postinng on the pro forum. =)