It won't be like the past years because the race is split into two days - which means the potential of double the runners = 40,000 runners. Also, many districts in the south are out of school until Jan 9th. That makes a great combo vacation of race and parks. Last year we went for the race, long weekend style. Now we are going for the full family style, entire week before the race. I am hoping it will be quiet, but I'm not counting on it.
ps Saturday is Half and Family Races. All starts and finishes at EPCOT. May have some parking issues at EPCOT in the morning but I wouldn't think that other than the travel issues early in the morning it will be too bad. Sunday will have more issues since the race is longer and affects all four parks, but I still don't think MK will have any problems since it is the first park they visit.