Wild Rice Dressing with Roasted Grapes and Walnuts

Name: Wild Rice Dressing with Roasted Grapes and Walnuts
Ingredients: 6 tablespoons (3/4 stick) butter; 1 cup chopped shallots (about 4 large); 1 cup chopped celery (about 3 stalks); 2 cups wild rice (about 12 ounces); 4 1/2 cups (or more) low-salt chicken broth; 1 tablespoon dried thyme; 1/2 teaspoon coarse kosher salt; 1 cup long-grain brown rice; 1 1/2 cups red seedless grapes (about 8 ounces); 1 1/2 cups green seedless grapes (about 8 ounces); 2 tablespoons olive oil; 1 1/2 teaspoons balsamic vinegar; 1 1/2 cups walnuts, toasted, chopped; 1 tablespoon finely grated orange peel