We did this last year. We checked out late, went to Downtown Disney, picked up a few last minute souvenirs, and had lunch. Then, after doing some more browsing around, about an hour or so before ME was scheduled to pick us up, we took the bus back to the resort. You could also take a bus or other transport to Magic Kingdom (if your resort isn't on the monorail line), then take a little trip on the monorail and visit some of the other resorts just to look around.
They will hold your luggage and carry-ons for you, then get them out when it's time to check in for your flight and ME. We were at Coronado Springs and it was a very smooth process, hoping it's the same this year at Pop!