Serve as an appetizer, or serve it alongside the meal. Make the hummus a day or two in advance, and plate it and load it up with all the toppings just before serving.
Bake the pita chips a day ahead and keep in a sealed container. Chop and prep relish a couple hours ahead, if necessary.
A day before, prep the chicken and marinate the skewers, and pop the skewers on the grill (or the oven) the day of your gathering.