Thanks Travel K--that's exactly what my friend in/near Perth suggested--and looking around there seem to be a lot of day trips and/or short 2/3 day excursions around that area.
One thing I'm wondering--how much of this do I need to plan in advance? I would assume that it's best to get flights booked in advance of arriving in country--I've traveled to many countries (primarily in Central and South America where it's common to book excusions at the last minute...) and I'm also notoriously indecisive.