OK, finally got a bit more time....
On the jet lag front, it's not that bad coming here from the US. Just make sure you don't take an afternoon nap on your first day of arrival, have as late as night as you can and a couple of beers. Normally next day you're then fine. But watch out for the return journey, which is normally a killer. It takes me 4 or 5 days on a trip to the US to settle into the right time zone!
Jet lag probably won't be an issue for us in NZ if you get over it in Aus. It's only a two hour time difference and a four hour flight. Not a big deal.
For diving the Poor Knights, I definitely second the Dive! Tutukaka option (
www.diving.co.nz)- they are the best operator for visiting divers and will treat you well. Their rental gear is well maintained and would save you carting around two wetsuits. Expect water temperatures around the 17-19 degC mark in NZ at the beginning of April. We're already starting to cool off for winter.
To get to Tutukaka from Auckland, you've got two options - hire a car or get a bus to Whangarei. A quick note on Maori pronounciation.... this is pronounced Fvung-a-ray! Dive! Tuts offer a free (I think) pick up service from Whangarei. Accomodation boils down to the motor lodge in Ngunguru (incidently, the fish and chip shop here does the best mussel fritters in the world) or the holiday camp in Tutukaka itself.
Dive! Tuts only do day trips, which really is the most flexible option. If you want to look into liveaboards your two options are Pacific Hideaway (
http://www.divenz.co.nz/) or Ocean Blue (
http://www.oceanblue.co.nz/). They kind of suit different markets - Ocean Blue is a bit more of a luxury operation and there is nothing about the Poor Knights that Glen Edney doesn't know! Saying that, Mark and Denise who run Pacific Hideaway are also very knowledgeable and a great laugh. Both of these boats fill up real quick, so book in advance.
To be honest, a week straight of diving the PKs would probably start to get a bit samey! I'd definitely look into diving some other areas as well. A week is going to be a bit tight to see more than two areas, though, so I'd suggest a Northland focus including a trip out to the Rainbow Warrior - one of my favourite dives in NZ! For a RW trip, the best option is probably going out with Gary from the Matouri Bay campground but you might find that he isn't able to guide depending on how many people he has on his boat etc. It's a 15 minute boat ride from Matouri Bay as opposed to at least an hour for the other charter options based in Paihia. Paihia dive have recently bought a new boat and I've heard bad things about it - fast, but no tank racks and a pig to dive from. Have a look at going out with Dive North (
www.divenorth.co.nz) if Gary can't guide you on the RW.