These days, we have to cope with a variety of eating patterns- low carb, vegetarian, wheat free- when putting together a party menu. So, the first thing is, do you know your guests well enough to know whether any of these apply?

Potatoes are about right. 10 pounds ham if thin sliced, 12 if thicker.
2 gallons fruit salad, much less expensive to do yourself, or do fruit trays, prettier, hold better, leftovers more useful, see the fruit tray page. Strawberries and berries and some cut up melons, very simple.

Consider a large bowl, 2-3 quarts, of honey yogurt. Maybe a bowl of fancy granola for topping.

You want 5 9x13 trays of your casserole.

You might make quiches or impossible pies instead of the breakfast pizza, easy and fast, recipe on site, about 3 10 inch. These quiche-like pies are very attractive if garnished with halves of cherry or grape tomatoes before baking. If you do the pizzas, allow 1 small piece per person.

Recipes here:
ellenskitchen.com/bigpots/plan/brunch100.html

Consider adding an appetizer section:

2 pounds cheese cubes
3 pounds bbq sausage slices or little smokies
1/2 gallon deviled egg spread or spinach type dip, 2 pounds crackers
mini muffins, mini quiche or spirals, about 60

Here is a beverage selection that would be lovely:

Orange Juice, 3 1/2 gallons)
Champagne, 1 case,
One 2 liter bottle of each - cola, diet cola, sprite, ginger-ale
1/2 gallon iced tea sweet tea)
Coffee, 1 pound
Decaf coffee, maybe 15 cups
1 1/2 quarts 1/2 & 1/2, 1 pound sugar, 3 varieties artificial sweeteners, maybe shakers of cocoa and cinnamon, and a bottle of Italian flavoring syrup or flavored cream?
Hot Tea, a dozen cups, tops, many varieties offered, 3 lemons in wedges