Don't listen to Disney.
Listen to kaytieeldr. Not simply because I'm (almost

) always right, but because
I did this exact thing a couple of years ago (goofy4tink - 2008? 2007? by the way, I offered to pick her up at the airport, but in the interest of research for this forum about which she cares so much, she opted for the Mears Shuttle).
Each Guest with a Disney resort reservation is entitled to one DME ride from the airport to their Walt Disney World resort on or after the day their reservation starts, and one ride from their WDW resort on or before the day their resort reservation ends. Period.
So, yes, the OP's husband can ABSOLUTELY use Magical Express to get to the airport to pick up a car. I did. The same category car that would have cost me $250 onsite, was $84 at the airport. Now, I was able to make my DME return reservation when I checked in at the Welcome Center for my WDW-bound Magical Express trip.
But - while being truthful would be best, less confusing for the CMs would be for the OP to simply find a flight that leaves MCO about three hours after her husband plans/wants to pick up the rental. Call Disney. Use that flight number and information for your husband's reservation. Voila!
Do you mind if I ask - did you call Disney (e.g. resort reservations, travel company) or did you call Magical Express directly? The toll-free phone number for DME reservations is in one or both of the Magical Express "sticky" threads at the top of this forum. I never remember the number, but the area code is 866.