I looked up the manual and it says your smoker has a capacity of 160# of butts/shoulders. Assuming a yield of 50% which should be safe, one full load will give you 80# of finished meat after bone removal.
Assuming 6oz servings, you'll need ~56#, so one full load will do you, with a little left over for wedding crashers. If you've got a bunch of heavy eaters or don't plan to do a bunch of sides, go with 8oz per person. If there are a lot of kids coming or you know the crowd to be lighter in their appetite, go with 5oz per person.
One labor saving tip: you should be able to find boneless, un-netted shoulders from a commercial food supplier. If you can find these, the work of pulling your load of meat will be reduced to almost nothing. Also, the yield on these is much higher, so you'll cook less. Enjoy the party.
http://www.thewestcoaststore.c...-206_smartsmoker.pdf