You have a few options...
1. rent a car
2. book the Mears shuttle
3. hire a car service
4. take a cab
Disney doesn't run any buses between MCO and the S/D. They don't own the S/D, so it isn't up to them to get guests around. The S/D do pay Disney to provide buses to the parks for their guests though...so that isn't an issue.
I have used a car service to the S/D as well as the Mears shuttle. The shuttle is about $35 r/t pp....I think. It's $19 one way, so imagine that it is in the area of $35 r/t. You can book a car service for about $100, plus tip though. If Mears is $35 pp, that will be $70 for both of you, then add tip....it may be about $30 cheaper than a car service. I would use the car service...they will be in baggage claim, waiting for you then go directly to your resort vs having to checkin at the Mears area, possibly wait 20+ mins for your ride, then make multiple stops along the way. Don't get me wrong...it worked pretty well for me last Sept, but I was by myself, had carryon bag only and wasn't concerned about getting to the resort quickly!!