Heat grill. In a small jar with a tightly fitting lid, combine olive oil, lemon juice, mustard, sugar, garlic, Greek seasoning, salt, and pepper. Shake to blend. Transfer 1-1/2 tablespoons to bowl, add shrimp, and toss. Combine remaining dressing with garbanzo beans.
Grill shrimp, turning once, until cooked through, about 3 minutes per side. In a large bowl, toss together spinach, tomatoes, cucumber, olives, and grilled shrimp. Toss with marinated garbanzo beans and dressing. Sprinkle with cheese.