Yes I think this recipe can definitely be multiplied for a larger crowd! If you do that, I would recommend adding the pumpkin puree, Baileys, vodka, and pumpkin pie spice to a large drink container and whisking very well with a metal whisk until the pumpkin puree is incorporated. I would then add ice to the container. For the glasses, you could rim them in advance then provide people with whipped cream and additional pumpkin pie spice for topping off their glasses. If made in advance, make sure to store the whisked drink in the refrigerator and re-stir before serving.