Yes, you have to reserve DME in advance whether or not you use the luggage delivery part of the service.
As far as your return to MCO....if yo uare flying on a 'participating airline' you will be able to check your bags right at the resort and get your boarding passes issued. But....the counter is only open from 5:00 am to about 1 pm. You have to be checked in, with the airline, no less than 3 hrs before your flight, so if you have a really early flight out (before 8:00) you won't be able to use this service. Or one later in the evening.
If you don't use this service (RAC) you would use DME as instructed to. The day before you are to check out of your resort, you will have a note from DME left in your room (under your door) telling you what time you are expected to show up for transport back to the airport the next day. It is usually about 3-3 1/2 hrs before your flight departure. So...take your bags (all of them) with you to the bus. The bags will go underneath the bus, you will hop on and off you go.
Here's the thing...if they give you a time of, say, 1:00 pm, be there no later than 12:45 pm. That time of 1:00 is when the bus leaves...so you will need to be there early. If you have to go to bell services and get bags out of storage, plan on leaving extra time to get to the bus...it can take up to 20 mins to get those bags out of storage. Not all the time but it can happen!
Phew! I am fine since Jet Blue departure for that day is 12h50, thanks a bunch