Hot chocolate for a crowd of 12, made from scratch at home, carried hot in a thermos, with a toppings bar at the lot. Kid-friendly. About 25 min of work.
Hot apple cider for a tailgate that serves 16: simmer it with spices at home, carry it hot in a thermos, add bourbon or rum by the cup. About 45 minutes.
Big batch margaritas for a crowd of 16: fresh lime, tequila and orange liqueur mixed the night before, poured over ice at the lot. About 25 min of work.