Any or all except one person in the room may leave via Magical Express before check out day.
They will need written confirmation with bus departure time in hand the morning of the day before the day they will ride Magical Express back to the airport. Make last minute additions, changes, corrections, etc. that morning of the day before the day they will ride DME, before heading for the parks.
Shoot to be back at your resort an hour before your DME bus time back to the airport. This will prevent the anxiety and raising hell to get on the bus after yours you missed.