Base upon a benchmark of 35 to 40 guests. 2 pounds of ice. Some folks prefer water. There is a water fountain near by, but perhaps a pitcher of water could be provided. Keep selection simple.
Simplicity also encourages others to volunteer.
Basic hospitality is the idea, visitors are not looking for a full spread. A bag of apples and a tub of apple caramel for dipping. Roughly 50 cents to a dollar per person. Placing a table near the kitchen Make waste baskets available Tablecloth is an added touch only if you want. Rule of thumb , allow adequate space for traffic flow and access.