I've gone Labor Day weekend a few times (2008, 2009, 2010) and found the crowd levels to be very low...I went to MK one year on labor day and it wasn't crowded at all. To tell you the truth, the only day MK felt crowded to me was Sunday. I believe we went on Sunday in 08 and MK seemed crowded. But it wasn't that bad. I love going Labor Day week as every time I've gone there were no crowds...I think you should be fine either day.