Cost-cutting seems to be the theme for reunion planners these days. One year my family had a less formal banquet at a really nice all-you-can-eat buffet-style restaurant. It turned out to be one of our most memorable banquets. The food was excellent plus we had a private room at a reasonable price! If you just have to have the banquet at a hotel, then try to hold the event earlier in the day, like a breakfast event; it will cost less. Also, try to look for free events (festivals)in a nearby city or town.
For younger reunion attendees, look into the cost of having a family movie night, bowling, or skating event(always ask for group rates).