With all 3 of these, especially the shrimp, you may want to do a mix with veggies, to the likelihood of many spoonfuls on any particular plate. Laos, put the shrimp last in the serving lines (assuming 2 lines or a double sided line for 150).

meatballs, 18 pounds small, 4-6 quarts gravy or sauce
sliced chicken breast, 20 pounds boneless skinless
shrimp, 30 pounds shelled, maybe with onions and peppers or tomatoes sauteed in?