Cut chicken and pork into 3- x 1/2- inch strips. Cut beef sirloin into thin long strips. Peel shrimp, and devein, if desired. Place chicken, pork, beef, and shrimp in separate bowls.
Whisk together soy sauce and next 5 ingredients. Drizzle evenly over bowls of meat and shrimp; toss to coat. Cover and chill 30 minutes. Soak skewers in cold water to prevent burning.
Thread chicken, pork, beef, and shrimp evenly onto skewers (10 skewers of each ingredient).
Grill, covered with grill lid, over medium-high heat (350° to 400°) 1 to 3 minutes on each side.
Arrange skewers on a platter, and serve with Spicy Peanut Sauce.