Arriving in Orlando, bring your carry-ons to the welcoming area. Larger items must go under the bus.
The published rule was 10 days advance reservation going to Disney, one day advance notice going home. They might allow shorter notice, doesn't hurt to ask.
Oops, sorry, I was thinking of just the airline checkin portion of the return trip. For the ME return bus, Seashore has posted the info. We do the checkin minus the bus ride back.