I suggest you add appetizers and here's why:

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. For your Southern Sunday dinner type menu, you could do classic relish trays (2, top of the veggie tray page) and deviled eggs.
One appetizer service area One serving area is needed for each 100 guests. For 150 people you will need about 10 gallons of lemonade or punch. This will also cut down on the sodas after.

Now, on to dinner for 150:

roast, 1 pound raw boneless per 2
fried chicken, 1 piece per person
corn,30 pounds
green beans, 30 pounds
turnip greens, 20 pounds
mac and cheese, 10 pounds dry pasta, 1 quart sauce and 1/2-1 pound cheese per pound of pasta
creamed potatoes, 35 pounds potatoes to start

cornbread muffins- 160
rolls- 160
Add butter, 5 pounds

Drinks
Tea, about 10 gallons, 1/3 unsweetened
water, 2 bottles per person

cokes,
sprites,
dr Pepper
Use the beverage planning page, do for 100, get some sugar free

wedding cake is lemon, you don't say how large? It matters
chocolate cake, about 80 servings