I assume you're talking about your flight HOME from WDW and using DME for your trip from the resort to MCO.
You will receive information about your scheduled pick-up time in your resort room the day before your departure. In general, you should expect that your pick-up time will be approximately three hours before your scheduled flight departure. In your case, with an 8:00 a.m. flight, that would mean a pick-up time of about 5:00 a.m. and you would need to be at the stop and ready to go about 10 minutes before that.
As far as your bags go, you likely will have to take them with you on the bus and check them at the airport. For one, SWA currently only "participates" in the Resort Airline Check-in service (RAC) through a pilot at POP and not at any other resorts. Even if you are staying at POP or SWA expands to other resorts by your vacation date, your flight is too early (JUST!) to allow you to take advantage of RAC. That's because you have to have your baggage check COMPLETED no later than three hours before your scheduled departure time and the RAC desk doesn't even open until three hours before your flight, so there's no way that you could get it done in time. (What's more, you'll have to be out front for your DME pick up before 5:00 a.m., so you can't be inside checking bags when they open for that reason too.)
Fortunately, taking your bags on the bus ande checking them at the airport isn't a big deal. Sure, it's not as convenient as RAC, but it's not the end of the world.