Avocados Stuffed with Shrimp and Crab Salad

Name: Avocados Stuffed with Shrimp and Crab Salad
Ingredients: 1 pound cooked shrimp, chopped; 1 pound jumbo lump crabmeat, picked through for bits of shell; 1/2 cup mayonnaise; 2 tablespoons chopped fresh parsley, plus 1/4 cup whole leaves; 6 to 8 radishes, finely chopped, plus 2 thinly sliced; 2 stalks celery, finely chopped, plus 1/4 cup thinly sliced; 2 small shallots, finely chopped; Juice of 2 lemons, plus wedges for serving; Pinch cayenne; Kosher salt and freshly ground black pepper; 4 large avocados, well washed; 8 cups baby arugula; 2 tablespoons olive oil