1) A variety of activities (both energetic and low-key, as well as, indoors and outdoors),
2) A variety of dining choices (upscale, low-cost, new, familiar, and highly-recommended), and,
3) Convenient access to both activities and dining (within walking distance, by public transportation, or a short cab/car ride).
Over many years of traveling with family and friends, I have found this combination always makes for an ideal group trip.