MANGO SALSA: Mix all ingredients into a small bowl. REFRIGERATE OVERNIGHT.
POBLANO SAUCE: Preheat oven to 500°F On baking sheet, roast poblanos, turning once until charred, about 15 minutes. Place in paper bag and seal. let cool. Scrape blackened skin off the poblanos. Remove stems and seeds.
In blender, puree all sauce ingredients EXCEPT cilantro. Transfer to saucepan over medium heat and simmer 10 minutes to thicken slightly. Cool to room temperature. Stir in cilantro. REFRIGERATE OVERNIGHT.
PEPPERS & ONIONS: Heat oil over medium heat in a large skillet. Add onions and peppers. Sauté 8-10 minutes. Remove from heat and transfer to a small covered bowl, REFRIGERATE OVERNIGHT. (they will cook more when re-heated the next day).
MARINADE & TRES DIABLOS: In food processor, puree all marinade ingredients. Cut steak crosswise into 4 pieces (less cook time). Place steak, chicken, and shrimp in 3 separate plastic bags and add 1/3 marinade to each. REFRIGERATE OVERNIGHT.
THE NEXT DAY: Remove meats from marinade (discarding marinade). On an oiled outdoor grill over medium hot coals, Grill chicken 6 minutes per side, and for the steak for 3 minutes per side for med-rare. For the shrimps, use either skewers or a (grill friendly) skillet. Shrimp will take about 5-6 minutes to cook. Wrap tortillas in foil and also heat on grill, turning after about 3 minutes.
turn off the grill if gas, remove everything from the grill except tortillas until ready to serve. (If using wood or coals, move tortillas to a side of the grill away from coals). Transfer steak and chicken to cutting board, cover and let rest 5-10 minutes. Remove shrimp and cover with foil to keep warm. NOTE: Now is a good time to set up the table and also to re-heat the peppers and onions (you can use the microwave).
Set the table buffet style with the assortment of onion pepper mixture, poblano sauce, and mango salsa (you can also add sour cream and guacamole to the table if you like).
Thinly slice steak and chicken diagonally across the grain (on the bias). Keep shrimps whole (removing from skewers if used). Add the tres diablos to the buffet table along with the warm tortillas and ring the dinner bell!