Toss shrimp, carrots, peas, corn, and 3 tablespoons vinaigrette in a medium bowl to coat. Season shrimp salad, to taste, with salt and pepper. Place 1 avocado half on each of 2 plates. Divide shrimp salad on top of avocado halves. Drizzle the remaining 1 tablespoon of vinaigrette over avocado halves and serve.