I recently cooked brisket and 3 sides or a reception that had 150 invited guests. My first event over 24 people. After much research into catering for a wedding, I discovered that on average only about 75% of invited guests attend. And of those, not everyone likes what's served, so you don't even have to account for 75%. But being my first I wanted to be prepared in case all 150 attended. Well, sure enough, only about 100 (at most) showed up and I had more leftovers than I knew what to do with so I ended up giving briskets and gallons of sides to the immediate family of the bride and groom.
Some things I learned beforehand that served me well. 1) Make easy sides (cold sides are much easier to handle) and sides that appeal to as many people as possible. Based on my research I chose a pasta salad and a baked potato salad since they could easily be made 1-2 days in advance, were served cold, and I had plenty of refrigeration at the venue. I found a southwestern pasta salad that was really good and made Guy Fieri's baked potato salad. Both were a hit, easy to make and easy to transport. I 'outsourced' the beans to a friend and told them they had to manage the temperatures for them since I'd have the single stove covered up. I based the serving quantity on side at 1/4 cup per person. The more sides, the less they'll get of each.
I used the following link to up-size my side recipes. http://www.webstaurantstore.com/recipe_resizer.html
For the briskets, I planned on 1/2 lb per person (uncooked weight to allow for shrinkage). That came to about 8 briskets. I cooked well in advance (2 months out) and over the course of 2 weekends so I didn't over extend myself. I trimmed some fat prior to cooking, then separated the flat and point to clean up some of the fat in between after they were done. I then put the 2 pieces back together and vacuum sealed them - separating them allowed for smaller packaging and placed in the freezer. If you're doing pork butts I'd suggest removing any bone or un-edible fat before vacuum sealing.
4 days prior to the reception, I put the briskets in the refrigerator to begin thaw. To heat up for the reception and starting 5 hours prior to the event, I used 2 large canning cookpots that would hold 3 briskets each, heated on med heat for about 2 hrs maintaining water temp at abouto 150 to 160 (must be above 140). Pulled them, put them in a cooler and covered in towels to maintain temp, then did the same for the last 2.
I waited until the last minute to pull from the cooker, slice, and put on a warming tray since I wanted to be sure to serve them at optimum moistness, temp, etc.
Create a schedule of every event, time, etc you have to do on the prep, cook and especially for the wedding day.. I even scheduled when I was going to costco for supplies 2 months prior. Create a task list and assign others to assist and make sure they know when, what, etc and that failure or lateness is not an option.
Get help on the serving. We ended up hiring workers from the venue to serve, which meant I just had to heat the meat, slice it and hand it over to them. They took care of all the sides and drinks (oh yeah, I had to buy drinks too). If you're having friends or family help serve are participate, assign them exactly to what you want them to do (ie you're responsible for serving side #1 and assisting with filling glasses with tea). Assign someone to supervise them to make sure they're not ganging up in one area or playing with their phones.
Other than all that, it was a piece of cake. My even was for my step-daughter and her to-be husband and it turned out really great. The bride and groom especially liked all the leftovers I gave them.