I haven't found the Whaleback greens to be majorly slow. The greens roll reasonably well there for public, just a tad slower, maybe a medium pace like maylands with a bit of slope but not much.
Hillview was looking really good two weeks ago. The greens felt like they had been rolled, as I was putting the ball off the green on the 5th and 7th!
Veeman has quite a bit of matchplay experience playing at Kwinana, and Yoss has played Wanneroo a few times, Veeman also.
So Wanneroo or Kwinana would be good choices for this semi final IMO, but it's up to big daddy V and the Yossmeister.