If you know prior to your trip that some people will be leaving early you can set up their DME reservations that way when you make the reservations. If you're not sure they will be leaving early or plans change part way through your stay, another option besides calling DME directly is to talk to someone at the hotel's Concierge desk. It's been a few years since I've done it but when we needed to change our DME reservations part way through a stay, I asked the hotel Concierge what I needed to do and he picked up the phone and made the change for us.