Thank you for your participation! Bringing snacks can be as simple or elaborate as you'd like. What matters is that you're helping out. Plan to arrive 15 minutes before the service to get things ready, make coffee, etc., and to stay after for about 30 minutes to help clean up and wash dishes. A detailed instruction sheet will be provided so you will be prepared.
Some ideas for simple snacks include bagels and cream cheese, a box of doughnuts cut into halves or quarters, cheese and crackers, a fruit and/or veggie tray, a box or two of cookies, etc.
Ideas for a slightly more robust snack might include a cake or some pastries, a variety of quick-breads (home baked or store-bought), cured meats with cheese and olives, hot or cold appetizers/finger foods, etc.
And if you're really feeling it some ideas include deli sandwiches, tea sandwiches, pasta/pasta salad, meatballs in sauce, etc.