You also are serving shrimp, and it is a catering truism that you never have any shrimp left. Everyone eats all they can get. So if you make skewers of shrimps, some people will take 2 or three. Grilled, they cook much faster than any of the other meats.

So you have to make some decisions. If the budget is limited, consider serving the shrimp as a chilled cocktail, possibly Mexican style, in the sauce with other additions, pre-portioned into individual containers such as the small clear plastic wine/punch type glasses widely available. Thus, people will take just one each, and you can get away with 1 pound peeled for each 4-6 people. A recipe is included here for you.

Or else, allow 2 pounds unpeeled (take off the legs, but not the shells) for each 5-6 people for skewers. PLUS 1 pound beef for each 4-5, PLUS 1 pound chicken for each 5-6, PLUS 1 pound pork for each 6. Kabobs are a meat intensive meal.

MEXICAN SHRIMP COCKTAIL
"Coktele de camarones" served in pretty see through glasses with tostados and saltines, it is meant to be eaten like a soup and not a dip.
8 appetizer portions, 3-4 main portions

2 tablespoons lime juice
2 teaspoons olive oil
2 small or 1 large avocados, diced
2 cucumbers OR 1 English cucumber, peeled, seeded and chopped
2 tomatoes, diced
OPTIONAL 1 medium red onion, chopped OR small bunch green onions
1/2 bunch cilantro, chopped
OPTIONAL 1 jalapeño, seeded and chopped
1 pound large shrimp, peeled, de-veined and steamed *
Up to 1 1/2 to 3 cups Clamato juice(may use spicy or plain V8 if desired); to taste for amount of wetness desired.
3 limes, quartered
Tabasco sauce
OPTIONAL vegetable for garnish

Mix all ingredients except the limes and Tobasco in a large non-reactive container. Let sit for a few hours in refrigerator, or overnight. Portion into individual servings. Garnish tops with a bit of diced avocado, or cilantro sprigs. Serve with limes and Tabasco sauce.