You can make Hummus, Tzatziki and other dips like Muhammara a day ahead. Or, you can use store bought also. Keep it refrigerated in an airtight container. Before serving take out of refrigerator a few mins or an hour earlier so that it comes at room temperature. Falafels can be made the same day or a day ahead. I prefer making it the same day. Store in a container with airtight lid. Reheat in oven or air fryer before serving. You can arrange the platter a few hrs earlier and cover with cling film and refrigerate. Let it come to room temperature a few minutes before serving.