In a large punch bowl, add the dark rum, spiced rum, and white rum.
Pour in the pineapple juice, orange juice, and lime juice.
Stir in the pumpkin puree until fully dissolved.
Add simple syrup or cinnamon syrup, grenadine, pumpkin pie spice, and bitters (if using).
Fill the bowl with ice to chill and dilute slightly.
Slowly pour in ginger beer or club soda for a fizzy finish.
Stir well and taste. Adjust sweetness or spice to your preference.
Ladle into glasses filled with ice.
Garnish each serving with fruit slices, a cinnamon stick, and a pinch of grated nutmeg or a cherry.