I think you are cutting it too close.
If your flight is on time, it lands at 2:30. Depending on where you are seated, and how large the plane is, it could take a half hour or more to get off. So 3:00. Then a 15 minute hike to DME. Where you may or may not have a line to have your tickets scanned, and then may or may not have a wait for a bus. So if you are lucky enough to get right on a bus and go you are now at around 3:15 and just departing the airport.
If you are really lucky and your resort is the first stop you are now at around 4:00. Only an hour ahead of when you should be checking in for your ADR. And you still have to check in to your resort, take care of your bags, and catch a ride to the Poly. A taxi would be best, but if you are planning on using a Disney bus you first have to ride to the Magic Kingdom and then either monorail, water taxi, or walk over to the Poly. So conservatively it is now already 5:00. And that is if everything goes your way.