Butternut Soup
Mashed Potatoe Casserole
Marinated baked chicken
Glazed Carrots
Ice Tea/Lemonade
Coffee/Tea

Could you give an idea of how much of each we will need t feel 180 people?

First I want to suggest an appetizer table:

Before the Buffet; Why You May Need an Appetizer Table
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; 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 One serving area is needed for each 100 guests.

Now, on to dinner:

Butternut Soup- buffet, do 4 gallons per 100

Mashed Potato Casserole, 45 pounds potatoes per 100- see the freezable, holdable mashed potato recipe on Big Pots

Marinated baked chicken- depends on what kind of pieces, the plan for 100 chicken section is very specific, please see this

With 200 people, you need a second dish that can serve as an entree for people who don't eat chicken. This could be a veggie casserole with cheese- 3 gallons per 100

Glazed Carrots- 22 pounds per 100

Ice Tea/Lemonade about 12 gallons tea, 1/4 unsweetened and 10 lemonade
Coffee/Tea
See the beverage planning page. Do dinner level coffee for all.