Look here:
www.ellenskitchen.com/bigpots/plan/saladbar100.html
for any other items, you would do 1/2

Mixed greens pre-cut 3#
Romaine 2#
Good for greens
Carrots, fresh slices 3# raw- 2 plenty
Cucumber, fresh, sliced 6# raw-4 plenty
Cheese, shredded 1.5#-OK
Croutons 20 oz- 2 pounds small
Chicken, grilled, diced 3#- OK
Ham, diced 3#-2 plenty
Peas, green frozen/thawed 2#- 4 cups
corn 2#-4 cups
Tomatoes, cherry 4#- suggest grape, or 5-6 pounds cherry
Consider adding:
chopped eggs, 18 hard cooked
avocado, cubed. 3-1/8 lbs ready to serve, which is 4 1/2-5 pounds as purchased, would allow 2 tablespoons per person
Beans- suggest you do both kidney beans and garbanzos, about 4 cups each, might be marinated

Ranch dressing 1 qt- suggest do 1/2 low fat Ranch
italian dressing 1 qt- pint sufficient
vinaigrette 1 qt- pint sufficient
Consider pint exotic- blue cheese, honey mustard or some such

rolls 12 dozen- you only need 8 pounds. Get good ones! Consider baguettes, Italian, French, ciabatta, etc
butter 4#- 3 plenty

raspberry lemonade 4 gal
Suggest 2 gallons unsweetened tea herbal tea blend or other non-sugar non-water
water- pint per person
After lunch there will be a dancing/cookie reception for 1.5 hours for probably 150-200 people. We're thinking 5-6 kinds of cookies 12 dozen each.
-Plenty. Have some nut free and some chocolate free
strawberry milk, chocolate milk, and 2% - 2 gallons each.
Suggest you add more lemonade- You want 12 gallons total beverages for 150 people
Ice water-pint per person, If served in glass containers with spigots, you might consider slicing citrus into one and cucumber and mint into the other.

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