We just did this last month (from Saratoga Springs) and it was a little bit of a pain - mostly because DME just could not comprehend that we wanted to go back to the airport, but not for a flight - and yes, we knew DCL transport picked up from the resorts, but we didn't want to get to the port that late.
I called DME a couple of days before we left and they said we were set for an 8AM DME pick-up from Saratoga Springs. When we checked in (for one night only) I asked the concierge if our DME was in the system - it was not. So I called DME a second time right there in the lobby, they booked it, and it did show up on the concierge's screen. She printed the documentation out for us and we were set.
We got on our DME bus at 8 and got to the airport at...I don't know, 8:45? Told the driver we were going to the DCL pick-up and he told us what stop to get off at. The desk opens at 9, there were maybe 25 people already there so we hopped in line and got on the first bus. We were at the terminal by 10.
I'm glad we did it because we did get on the ship early (boarding group 2) but it was a bit of a pain to set up and a lot of bus time. The DCL bus ride itself was good though, and their video they play is like the old DME video (loved that)...not the new, awful DME TV. Next year we're planning on staying at the Hyatt in MCO the night before and heading down to get in the check-in line at about 8:30. It'll be way easier and cheaper that way.