This is not the least bit realistic. Fun, party cocktails is not at all an idea these people would have been familiar with. However, that is not to say they did not drink alcohol. A frequent shipboard ration of beer was a mind blowing gallon per person per day (man, woman or child). But they would have been low on supplies at this time, and though they grew barley, the fermenting process is so time consuming they probably did not yet have any ready by the time this celebration took place. Water was probably the beverage on offer.
But just because they were abstaining out of necessity, doesn’t mean we have to. This is the perfect use for any left over pumpkin and whipped cream you have laying around.
Mix pumpkin puree and heavy cream until you get a drinkable consistency. Then add whisky or bourbon to taste. Add a dollop of real whipped cream on top of individual drinks and top with nutmeg.