According to the Village web site, the only total road closure for Sunday's race will be Hwy 165 from Hwy H west to Corporate Drive (the turn at Culver's). Other roads on the course will be open to local traffic only.
Based on this, it would seem that Hwy H will be open all the way north and south, as will Hwy 165 going east and Green Bay Road. If you are coming north on H toward parking, be careful at the intersection of H and 95th street. Cars may be stopping there and there is a chance that they will stop (or block) northbound traffic since they expect most cars going to parking will come south on H then make the left turn onto 95th street.
There will likely be a lot less traffic if you go to parking via Green Bay Road, then turn west on 95th Street, and then into the parking area.