Welcome to the site Chris.
For large chunks of meat you have to cook according to internal temperature... not time, and to make it more confusing each piece of meat can be differant! I have had two near identical 10 lb. pork butts finish two hours apart before!
I don't know what size smoker you got, but my suggestion is to smoke all of them 1-2 days ahead of the party and then re-heat them the day of the smoke. Then there are no supprises of something not finishing in time! Click on the "forum" selection at the top of this page, then scroll down to beef or pork and do a search for brisket or pulled pork. (also there are some "sticky's" at the top of each forum as well).
This being your first time I would plan on foiling the meat when each piece hits 165° interal temp., then let it go all the way up to 190°. As each piece hits 190° pull it off the smoker, drain the juices out of the foil (save them!) and place it in a dry towel lined ice chest, and let it rest for 1 hour (minimum). - De-fat the juices and save them in the fridge, keep the beef and pork seperate. The pork can be shreaded and stored in ziploc bags, but leave the briskets whole.
Day of party pre-heat your oven to 250°, place shreaded pork in foil pans with 1 C saved juices and/or apples juice and place whole foiled briskets with 1/2 C saved juices and/or low sodium beef broth, in the oven for 4-6 hrs. Once the internal temp gets up to 165'ish. slice up the briskets and place in foil pan with juices and any remaining saved juices, also add any remaining pork juices to pork, turn oven to 150° and wait till you are ready to eat before pulling them out.
You can use the 4-6 re-heat time to get sides and stuff made!
Good luck! and take lots-o-pictures!
