You can do it either way, Fort Wilderness has 2 boat routes, one goes to the Contemporary, Wilderness Lodge and back, the other goes to the MK and back. I can imagine that the MK boat would be really crowded on NYE and you may have to wait on a second boat (which would probably mean adding on an extra 30 minutes as they run on about a 20 minute schedule and it's about a 10 minute ride); it's the only direct transportation between the Fort and MK, there is no bus.