What an exciting time. We will assume 90 people, since you don't want to run out.

This size party is at the max of what you can do in a home kitchen, and you have chosen a fairly oven-intensive meal. Day of, it will take 2 people in the kitchen and about 6 people to set up serve, and clean up the party. This should not be you or your mom or MIL, as all will be tied up with the wedding during the critical 2 hours before dinner.

veggie trays, see veggie tray page. You might consider doing 1 classic relish tray and 3/4 the deluxe fruit tray for 100, instead.
cheese, 1 pound per 12, some can be logs, balls, or spreads.
crackers, 1 pound per 12-15
pickle trays, about a gallon mixed total, these could be on the relish tray discussed above, some olives could be included.

prime rib, 1 pound boneless per 2 or 2 pounds bone in per 3. See the beef roasting page for a lot of tips on selecting and roasting. Be SURE to allow the standing time after roasting before it is sliced, it makes a big difference in quality.
halibut, 18-20 pounds, 3 ounce size servings. Have tartar sauce about 3 quarts
either mashed potatoes or baked potatoes, baked easier, purchase 2 cases of 40's or 60's from a produce supplier or restaurant supply. Toppings are discussed on the potato bar page. This can serve as an entree for any guests who don't eat meat, if you have a nice selection of toppings.
corn on the cob, please reconsider. This is a messy food to eat and people will be dressed up? About 20 pounds loose corn

caeser salad, do 1/2 the amount for 100, see the plan for 100 page
coleslaw, about 2 gallons, probably some left
greek salad, see the recipe under salads that hold, do 2/3 the amount for 100

macaroni salad, start with 5 pounds dry pasta. Rotini or bow ties hold better than regular macaroni.

You need dinner level coffee with the cake- see the beverage planning page.