In medium covered saucepan cook green beans in boiling water about 4 minutes, until crisp-tender. Drain; rinse under cold water; drain again.
Place beans in large bowl. Stir in tuna, the 1 cup cherry tomatoes, the 1/3 cup olives, onion, and 2 tablespoons mint. Add lemon juice, oil, and 1/8 teaspoon pepper; toss to combine. Stir in salad mix.
To serve, cut pits in half crosswise. Cut each half horizontally. Fill pits with about 1/2 cup tuna mixture. On each wooden skewer, thread a whole cherry tomato, whole olive, and mint leaf; spear filled pits. Makes 6 servings.