I'd check for a hotel shuttle, or see if the ART goes to your hotel -- I'd be really surprised if there was a hotel near the resort that didn't have some kind of park transportation.
You won't be able to walk into/through Mickey and Friends to get to the tram plaza, so your only option would be to walk all the way around towards the DTD/DLH parking entrance to Magic Way, and then through the back end of the parking lot to the tram plaza, which would be really far...and that's assuming that there are sidewalks or pedestrian routes that go that way, which I'm not sure that there are. Even if you could do it, it would be a really long walk.