Begin by preparing the vinaigrette. Whisk together the extra virgin olive oil, white wine vinegar, lemon juice, Dijon mustard, minced garlic, salt, and pepper in a small bowl until emulsified. Set aside.
Combine the cooked shrimp, crab meat, cherry tomatoes, avocado, red onion, cucumber, baby arugula, and mixed greens in a large mixing bowl. Gently toss to distribute the ingredients evenly.
Drizzle the vinaigrette over the salad and toss again, ensuring everything is lightly coated with the dressing.
Taste and adjust the seasoning if necessary. You may want to add more lemon juice or a pinch of salt.
Transfer the salad to a serving platter or individual plates. Garnish with fresh dill or parsley for an added touch of flavor and color.