You are looking at at least 2 roasters, 4 other kitchen people, and about 20 servers to set up, serve, and clean up this size party. Most will NOT be attending the wedding.

As for the meatloaf: it depends on how big the pig is!
Allow 1 person per pound for the pig weight, Then do meatloaf for the balance plus about 35- some people will take both- using the plan for 100 guide on this site.

Then plan a vegetarian option for about a dozen. A crock pot of Field Roast smoked apple sausages would be a good choice.

macaroni & cheese, 1 pound dry pasta per 10, 1 quart sauce per pound, 1/2 to 1 pound cheese per pound
potato salad, about 135 pounds potatoes to start
baked beans, 3 gallons (4 #10 cans or 8 pounds dry) per 100
lettuce salad, use the plan for 100 table, it covers dressings also
rolls, 2 per person
butter, 3 pounds per 100
sliced onions, 25-28 pounds
pickles, 3 1/2 to 4 gallons

I urge you to have an appetizer plan, as a pig roast is particularly prone to delays and surprises.

A self-catered buffet is a real challenge to the organizers, and things don't always come together as smoothly as hoped. By planning and setting up an appetizer area or "nibble table" which is ready when the guests begin to arrive, the cooks and servers have time to complete the arrangement of the dinner buffet. This is especially critical if there are children among the guests, or there is a wait before dinner, as at a wedding reception.

This does not have to be complicated. Three items, plus a punch, or two if one is alcoholic, are sufficient. Typically, include a fruit tray, a cheese tray and an attractive dip or spread, maybe a classic relish tray; or you can go with a dinner theme such as TexMex with chips, salsas, Texas caviar and guacamole; Italian with bruschetta or antipasto; maybe shrimps or other cold seafood, if budget permits.

One appetizer service area serves about 100 guests. You would plan 3 or 4.