Tim,
I love Lawsonia, and would highly recommend it, but a 3 hour round trip (if you are staying in Kohler) may not be something your party is up for. The Bull is a great option for convenience. After a slow start for the first 2-3 holes, the course really picks up and has several very strong holes. It is a tough track, particularly the back side which borders on brutal, but is on really good land by and large. The 2 times I've played it the conditioning has been outstanding. Erin Hills offers more of a belt notching experience, and is just a very interesting course. If you are looking for convenience, don't hesitate on the Bull. As I understand it, right now play at run at Blackwolf Run is the front 9 at Meadow/Valley and 5-13 on the River. The Bull is superior to the front at MV, but not as strong as 5-13 on the River - only one of the better stretches of 9 anywhere. Have fun!