Having each family bring and cook their own food is the simplest and least expensive option. There should be a main eating area so that although eating your own food, everyone is still interacting with other relatives. This is impractical when many of your family members will be travelling to attend your reunion.
Every family brings a different item whether it be hors oeuvres, salad, main dishes, dessert, drinks, etc. This is a great way to bring your family together and in a fun and cost effective way.
This is a more expensive option, however you can enjoy the whole experience without having to worry about organizing, cooking or cleaning up. You will need to make a reservation several months in advance and find a restaurant with a menu that offers many types of food.
By having the food come to you, you need to make sure there is a place to eat at your location large enough for everyone to fit comfortably. Although costly, it is less expensive than a restaurants because food is prepared in bulk. A caterer can provide you with all different types of food to meet the preferences of your relatives.
