In a large zipper-top bag (about 1 gallon), combine the chicken, garlic powder, cumin bell peppers, the juice of one of the limes, oil and one tablespoon of the cilantro. Shake well to combine everything and properly coat the chicken with the seasonings.
Transfer the bag contents to a large cast iron skillet (or barbecue pan) and place the pan on your pre-heated barbecue. Grill for approximately 20-30 minutes. You want the chicken to be almost done cooking.
Add the thawed, pre-cooked shrimp to the pan and continue cooking until all the meat and shrimp are cooked to your liking. The chicken should reach at least 165 F. on a meat thermometer. The total cook time is about 40 minutes, but grill times can vary greatly depending on your grill. So use your thermometer here to be sure.
If you prefer to cook some of the larger pieces longer than the rest, simply remove them from the pan and place them directly on the grill until cooked through.
Once everything is done cooking, transfer it all to a large bowl and stir in the avocado and the rest of the cilantro. Sprinkle some lime juice on from the remaining limes and enjoy.
Serve any leftover lime in wedges with the meal.
Please note that the nutrition data is a ballpark figure. Exact data is not possible.