I'm assuming you mean 2.5 weeks over there?? Or 2.5 weeks away from work - just that it will tkae you about half a week for travelling there and back and transfers, jet lag, etc. Anyway - for Australia, I would suggest somewhere pretty obvious like Sydney, as there's so much to see and do there. Melbourne's a cool city too, but I think for a holiday, Sydney edges it. From there you could travel up the east coast (by the way, I must mention that, given your time restraints, you should also consider internal flights as Australia is just so damn big - took me 4 hours flying from Perth - west - to Brisbane - east). Definitely worth doing is visiting Fraser Island, just off the coast of Hervey Bay in Queensland. This is the world's biggest sand island and you basically hire a 4WD and bomb about the island, camping and bathing in some beautiful freshwater lakes. A 2 day boat trip around the Whitsunday Islands - Airlie Beach being the mainland port for this - about 12 hours' drive north of Hervey Bay. Beautiful islands and beaches abound. Also good for some diving and snorkelling on the edge of the Barrier Reef (which around Cairns is also excellent for, if not much else). I would try and get to the 'Red Centre' too, so a flight to Darwin or Alice Springs to get to Uluru (Ayers Rock). One thing's for certain, I would try (if funds permit) to get an open ticket where you can fly into Sydney, for example, and out of Cairns - that way, you'll not double back on yourself, wasting valuable time.
Obviously I could go on as Australia is such an amazing place, but you have a time schedule to keep to and you want to actually appreciate what you do, so try not to do too much, otherwise you'll feel like you haven't stopped travelling for all of your holiday.
NZ is also fantastic - in fact, I preferred it to Oz, but since I'm at work, and since I have a tendency to waffle, I'll leave that for someone else to discuss and get back to doing some