Vickie.
The first thing I would ask when I find a wine I would want to drink back at home, is "
Are your wines available in Aus and how can I be assured of getting some?"  That way you won't have to carry many wines back.
I have no idea how you would go about freighting wines - perhaps you could have a chat to Roger Gibson at 
http://www.otagowine.com.  He sells Otago wines too and will ship overseas.  Also Tim at "Alexandra the Grape" 
http://www.thegrape.co.nz will ship to Aus.
As for which wineries to visit - the world is your oyster. Leaving Queenstown stop at Amisfield Lake Hayes (awesome 2002 Pinot Noir), then head into the Gibbston valley where it is worth visiting Chard Farm just to experience the road into it, the cheesery at Gibbston Valley is a good experience as is the restaurant, Peregrines Wines is must plus there are a couple of other around there.
Then you go thru the gorge to Cromwell where it is worth stopping at the 
The Big Picture and experience the 'film' and tasting, also the perfume room with all the 'Le Nez du Vin' scents to sniff.  The risotto was very good when I visited.
Here you have Bannockburn with Mt Difficulty, Felton Road and Olssens in the Felton Road and Carrick (fantastic platters for lunch) and Akarua in Cainmuir Road, which is very scenic. You have to visit Quartz Reef  and the Central Otago Wine Co in the old industrial centre - the latter makes wines for about 15 wineries and usually has a selection of four or five to taste, including Sam Neill's label. 
Head up the road toward Wanaka, not many wineries open up here but vineyard after vineayrd for the first 15kms. Or cross the river and head south past the Clutha Dam to Alexandra. I would visit Black Ridge - just to be amazed at the landscape the vines grow in if nothing else, but the late harvest gewurztraminer is rather yummy.  There are plenty of other vineyards around here. You will need to check the map to see which ones are open. 
If you do make it to Wanaka I recommend the spinach, cranberry and venison pizza at Tuatara (takeway or eat in) - perfect with Central Otago Pinot noir.
Cheers,
Sue