Coordination with event operations and other participating agencies will make or break the success of your event. Things can become complex if there are multiple UAS and/or multiple agencies involved in flight operations. Where possible, standardize on logistics if cooperating with other groups: metric vs. imperial units, lat/long format, communications setup, and so on. This will be especially important when dealing with manned aviation, who will have far less flexibility in their choices.
To help ensure operations run smoothly, designate a UAS Operations Lead or Air Boss to be the point of contact for all UAS operations and associated logistics throughout the course of the event.
As you plan, constantly refer back to your mission objectives and communicate any changes should they be needed.