Your portions sound right on to me, although I would do closer to the 48 lbs of pork butt- Teenagers can eat alot! This should give you 1 sandwich per person. If you want more than that you will need to increase your amounts.
Some people are like Slinkys, they are good for nothing but can still bring a smile to your face when you push them down the stairs.
Down to one lonely ol' Bandera.