You have to do the legwork for your specific reservation. Look at the rental companies you're thinking of, look at each way of doing it. There is never just ONE way they have of charging. Sometimes they need cars at Car Care Center, so it's cheaper to drop there. Sometimes it's different. You have to do the research; there's no way we can tell you what way will be cheaper. All we can do is tell you to check for your specific trip.
I think that a minivan with 7 people and luggage is going to be miserable, so I'd put a monetary value on not having to deal with luggage... Assuming you have a flight that lands before 10pm...... You could have one person take the minivan from MCO while everyone else rides the bus, or even have no one take the bus, but THAT is a subject that has its very own sticky thread
here.
Going back, you can use the RAC luggage service even if you're not taking DME. It's not even controversial, so it doesn't have its own thread.

It's totally allowed. So I would send the luggage on its way in the morning, then when it's time to go to the airport pile the people in the van and head back to the airport. (we weren't the hugest fans of DME in either direction, but that RAC service, wow was it awesome!)
But that's IF IF IF it works out to be that much less expensive doing MCO as the starting and/or dropping point.
Gotta work it out for your specific trip.
