If the guests are told to bring their appetites, you may want to eliminate grilled chicken from the menu. Chicken takes a long time to cook depending on the parts of the bird you are grilling. It is also not safe to eat an undercooked bird due to health considerations.
If you try to do a chicken, this alone will cause some people to get their food ahead of others. To ensure that no guest is left with an empty plate, choose other meats, or pre-bake your chicken in the oven as if you were going to eat it roasted, and then put it on the grill to reduce the cooking time.
Or roast it, and then just add smoky BBQ sauce, so that your grill is not taken up with a bunch of long cooking chickens and you have no room for anything else.
Remember to always preheat the grill. When people come in and see smoke rising from the grill they expect that you have already put food on it. Don’t surprise them with the smell of smoldering charcoal.