An event this size requires at least 3 experienced people on the grills in addition to about 10 to set up, serve, and clean up. At least 3 serving lines; 2 double sided would be even better.

Outside, increases the amount of food, self serve increases the amount of food, and at a BBQ people tend to pile meat on their plates if it is self serve. If you look at BBQ catering sites, you will see they almost always include sausage or chicken, because it is less expensive and fills out the plate. So I am going to suggest some tweaks to your menu.

1. BBQ meats (skirt steak, Cutlets and Loin of Pork)
Allow at least 1 pound raw beef per 3 adult persons= 75 pounds
Cutlets and pork loin (both pork), 1 pound total per 6= 38 pounds total
If you add sausage, up to 20 pounds, you can cut back on the beef by an equal amount. Prep this ahead with equal weight onion and pepper mix, it will help cover any slowdowns on the grills.
If you add chicken, allow 1 piece per person, cut beef 15 and pork 10. Using quarters? Cut apart after cooking.
And have servers SERVE the meats.
2. Pastas (Fettuccini and Penne with Toppings such as Broccoli, mushrooms, peppers, onions, Bacon and cheese); at least 6 pounds dry per 100. You can use the salad topping list below as a guide for the pasta toppings as well. Put a can/container of shake on Parmesan on each table. Put a squirt bottle of BBQ sauce on each table.
3. Sauces (Marinara and Alfredo) 1 quart per pound of pasta; usual is 2 /3 marinara, 1/3 alfredo. The Alfredo style sauce for 100 on this site holds well and the amount would be about right.
4. Rice (2 varieties); at least 5 pounds per 100
5. Potatoes (1 variety); at least 25 pounds per 100; half the people will take some. If this were my menu with rice and pasta, I would skip the potatoes and offer oven-roasted veggies, which can be made ahead and even served room temp, instead. Same weight.
6. Salads (Spring Mix and Roman Lettuce with 6 toppings such as bacon, onions, cucumber, tomatoes, parmesan cheese and croutons)

Make salad for 200 from the salad section of plan for 100.
www.ellenskitchen.com/bigpots/plan/quan100.html

Use topping amounts from the salad bar articles:

www.ellenskitchen.com/bigpots/plan/saladbar.html

www.ellenskitchen.com/bigpot/plan/saladbar100.html

Then add about 4 gallons of cole slaw, 2 gallons sliced pickles, and 12-15 pounds thin sliced onions- standard for BBQ's.

Some kind of bread or rolls- 10 pounds per 100 with all the starches, 2 pounds butter per 100.

Strongly suggest 1 crock pot full of vegetarian sausages for any non-meat eaters.