We do this most every trip with no problem. When you come back to MCO ask your shuttle driver to drop you at United checkin. You will be directly above DME and can take the elevator down. Most shuttles will take you to the bottom floor as well, but in our experience they go to departures first and to get to the lower level they must exit and come back around the terminal which takes a while. If you are the only ones and they will run you down there directly-great.