In a 5- to 6-qt. Dutch oven cook ground turkey, onions, and garlic over medium-high heat until turkey is browned; drain off fat. Transfer mixture to a 5- to 6-qt. slow cooker. Stir in next six ingredients (through seasoning mix).
Cover and cook on low 6 to 8 hours or high 3 to 4 hours. Turn off cooker. Stir in cream cheese, ½ cup of the cheddar cheese, and the bacon. Cover and let stand 10 minutes; stir until cream cheese is melted.
Top servings with remaining ½ cup cheddar cheese, sour cream, and, if desired, additional jalapeño peppers.