Good luck with this one. I think it depends on who you talk to in MS.
We traveled to Dis this past July. We were going to Daytona and dropping my parents off at MCO the following weekend. My thoughts were we'd drop them off, drop off the rental car and take ME to Dis. When I call MS, they said no. I was told you can only take ME on the day you arrive. However, I had been told something different last year by MS and sent a note through dvcmember.com to get the policy (one way or the other) in writing. Here's what I received dated 11/13/2007:
Hi Bridgett:
Thank you for contacting Member Services.
Yes, if you are flying in late and staying at the airport you can use
Disney's Magical Express Service on the next day. However, you must let
us know so that the necessary arrangements are made prior to your
arrival. Just take your luggage with you to terminal B level 1 of the
airport and your luggage will travel with you on the motor coach.
As for the resort airline check, The Resort Airline Check-In service is
operated by a third-party company approved by the Transportation
Security Administration (TSA) on behalf of the participating airlines.
If you have additional questions please contact us at 1-800-xxx-xxxx.
Sincerely,
Ruby