Most of the trails will be open the 1st day of racing, it is a downhill race. The 2nd day is the cross country race and the trails will be closed for the most part. But the race doesn't take all day and you can ride before and after. But you will probably want to hang out in town for the after race party anyway.... to much fun!!!
Make sure you hit the Swedetown trails in Calumet while you are up there.
"Get busy living, or get busy dying." Andy Dufresne in the Shawshank Redemption