Well, if you'll accept a response from someone who hasn't used DME for return-luggage-only but knows...
The Lobby Concierge has absolutely nothing to do with DME. There is a counter outside the front entrance to the right for both Luggage Assistance and Remote Airline Checkin.
Since you're flying home on a participating airline, you can simply check in at the RAC counter at least three but no more than twelve hours before your flight, and check your luggage through to your destination. The counter hours are 5:30 AM to 1:30 PM.
You need to have all members of your party there and all your luggage, and IDs for anyone of an age where an ID would be required at airport checkin. You do NOT need to board a bus back to the airport or, I think, even make arrangements in advance.
Note that if your flight leaves before 8:30 AM, you will not be able to check your luggage in at Pop, since there won't be that three hour window.