You need a large space that's decorated with opulence or comfort in mind depending upon the nature of the gathering, a large selection of beverages from wine to ale to mead to teas, juices, and coffees, as you requested sandwiches I assume you wish for people to be able to serve themselves rather than having a banquet proper, yes? So a long table to hold all of the food, a menu, Musicians, space enough for dancing, lighting for when the sun does set and cushions and washcloths enough for the orgy.