The front desk at any WDW resort or the guest services locations in the parks and at DTD will do the check in for you. Bring your confirmation number and a photo ID. You also can check in yourself on a Web-enabled cell phone at mobile.southwest.com. Another option is to arrange with a trusted (100 percent reliable) friend or relative to check you in from their computer.
SWA also offers Early Bird Check-in service for $10 per passenger. With EBCI, SWA checks you in automatically 36 hours before your flight and you don't have to worry about doing it.