We use the On-line booking through the Members web-sight as we always have our flights way after our rooms booked. Never had a problem with it and it saves a call to MS.
It works like it does for al the other resorts.
You put your yellow ME tags on your bags before checking them . You check-in at the ME counter at MCO and then get on the bus. Then your bags show up in your room a few hours later.
The day before you leave you get a time to meet the bus and go back to the aiport. If you are flying a particapating airline you can check-in at the BAgs location at the resort.
If a non-participating then you have to take your bags on the bus yourself.