Make slaw: Mix cabbage, cilantro, and onions in a bowl.
Toast chiles: In a small frying pan over medium heat, cook sliced chiles in oil, stirring often, until some turn reddish brown, 3 to 4 minutes. Transfer chiles to paper towels, using a slotted spoon; reserve oil.
Make spread: In a medium saucepan, cook butter over medium heat, swirling often, until golden, 3 to 5 minutes. Add ground chiles and allspice all at once and stir until foamy, about 10 seconds. Reduce heat to low and stir in pumpkin, cream cheese, and salt; cook, stirring, until cheese melts, 1 to 2 minutes. Remove from heat. Stir in juice; scrape into a bowl. Just before serving, drizzle with reserved chile oil.
Warm tortillas: Divide into 2 stacks, wrap in a cloth napkin, and microwave until hot, turning over once, 2 to 3 minutes.
Set tortillas, spread, slaw, pumpkin seeds, toasted chiles, and orange wedges on a tray and let diners make their own tacos, adding a squeeze of orange and more salt to taste.
*Buy at a Latino market. Or substitute regular-size tortillas.
Make ahead: For spread and slaw, 1 day, chilled. Toast chiles the day of serving. Microwave spread until hot, 3 to 4 minutes.
Note: Nutritional analysis is per serving.
Servings Serves 16 to 18 (makes 36) (serving size: 2 tacos)
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.