Season shrimp and oysters with seasonings. In a very large sauce pan, melt 2 tablespoons butter over medium/high heat. Turn the temp down to medium and add shrimp, scallops and cajun seasoning. Saute for about 4-5 minutes, then add spinach, mushrooms, garlic, green onion and salt. Saute until mushrooms and spinach soften, then scoop up everything in the pan with a slotted spoon and fold it in the sauce. If needed warm up the sauce, then pour it into heatproof dish, top with grated cheese, and place under a broiler until cheese melts. Stir the cheese in and add additional salt if desired. Serve with crusty sourdough bread for dipping.