What kind of firm acts as an expert in finding locations, securing dates, scheduling activities, and pulling together teams of facilities managers, caterers, security people, entertainers, and celebrities.

An event-planning agency.

Explanation:

An event planning agency is responsible for establishing a schedule, budget, reservation of the places where the event will be held, permissions, planning of the food offered, organization of activities, schedule, necessary permissions, parking, decoration, security and all other details necessary for an event to occur as planned and expected.