The only way to know how they will handle it is to call them. Reservations are guaranteed for the dates/times/location(s) booked and any deviation from that may incur an additional fee (or in some cases could result in a price reduction), but it's pure speculation until you call them as each rental company handles it differently. Call 800-654-4174 and give the phone agent the number off the top of your rental contract and they will be able to quote you a price for the revised date/location.