If you haven't been there NYE before, be aware that Epcot fills up very early and is closed. Last year, that was about 9:00 or 10:00 AM. They still allow resort guests in and others with 'special' New Year's Eve passes, but everyone else is turned away.
Also, beginning anywhere around 4:00 to 6:00 pm, there'll be signs at the exits stating if you leave the park, you are not guaranteed readmittance. I believe this is true whether you're a resort guest or not, but could be wrong on that.
Last year we drove from OKW to Epcot (figured the busses coming back would be terrible), but didn't count on the traffic. We went over about 9:00 am, and were in a traffic line for about 2-hours just to get into Epcot parking. All the people getting turned away were not very happy. In this case, our OKW parking pass was like Willie Wonka's magic ticket.
We're going again this year, but will definitely take the busses.
(This is where I bow to those who own at BWV.........) I may have to buy into Beach Club just to be able to walk to Epcot on NYE....)
Don't plan on doing any of the rides at Epcot that day. The lines are terrible. Test Track was over 3-hours, and ALL the fast passes for the entire day were gone by noon. All the other attractions are almost as bad. This is a good day for people watching.
Get in line early for your free hat and horn.
Have a great trip!