Here is some math and info...
For Pulled Pork, relatively cheap and easy, you need to figure 6oz per person for sandwiches, 8oz per for plated meat. Men will eat 2 sandwiches, ladies and kids one sandwich. For PP Sandwiches...
6oz PP X 90 people = 540oz PP / 16oz = 33.75lbs / .50 (50% yield after cooking and removing fat) = 67.5lbs Raw Pork / 8lb avg. = 8-9 Pork Butts. More if there are a lot of men. Add one portion per man.
Rolls... 90 X 1.5ea = 135rolls / 12 = ~11 to 12 Dozen
BBQ Sauce... 90 X 1.5oz = 135oz
Beans... 90 X 3oz = 270oz / 32 = 8.5 Qt of Beans
Potato Salad... 90 X 3oz = 270oz / 16 = ~17lbs Salad
Quite a bit of work plus you probably need a alternate meat like Chicken Leg Quarters for those that don't eat or like pork and Mac 'n Cheese if there are a lot of kids. If you like to cook it's fun. I did a Pig Roast (115 Pounder) for a combo Birthday party for the middle girl and Christening for the new Baby. There were 50 people plus I had 3 Pro Chef friends there backing me up...Still prep'd 3 days, 12 hours up with the pig and spent way more time feeding folks than Partying...Congrats on the Baby and Good Luck...JJ