Most battery chargers these days are dual voltage and work happilly on either 115v 60 cycles or the australasian 230v 50 cycle. I travel between NZ and the States and all I need is an adaptor to convert between your vertical flat pins and our angled version. Since two of my cameras were purchased in the States and have vertical flat pin plugs I have a 230>115v converter but if you look at the back of you charger and confirm the figures I started with you should only need the plug adaptor. You might need the converter for other electrical equipment you bring. My son who normally lives in the States bought one for some reason, run his laptop I guess, and gave it to me the last time he went back. If you do need one I would suggest either Dick Smith or Jaycar with their stores thoughour Australasia, similar to the American chain whose name escapes me at the moment
Personally I wouldn't take my DSLR on holiday and previous trips I have used a bridge camera though last time I got a M4/3 camera [GH2] which with its lens is almost as big as a smaller DSLR so if I wanted to leave something behind it would be the WA lens, not a big saving for sure, since most situations the wide view can be obtained, and often wider than the WA lens gives, by stitching several overlapping frames when one gets home.
This is adding weight but I have a notebook to download to and to make back-up copies. If your camera uses CF cards you will need a card reader, mine cost $17 from your chain store I forget the name of. First to download to the notebook and then to access the back-up SD cards. I also have a mini-tripod which in these days of image stabilisation rarely gets used but your lenses may not have it?
Edit ... to cover Australia and NZ in two weeks is going to be stressful and anything you can do to reduce the amount of gear/weight you can, thats photographic and personal, will be great. .... after several crossings of the Pacific I like to think I have it about right with just a 'school napsack' I bought in New Orleans to carry my camera, jersey, medication, toothbrush, inflatable neck pillow, underwear change ... and that is it. Also think about how you go through security checks with metal scanners.