I visited a friend in Sydney in January and there's quite a few great places you might wanna visit!
Of course there's the obvious; the Opera House, Harbour Bridge and all..
I personally reaaaally liked the Botanic Gardens (just by the Opera House) where I spent many hours just walking around and taking photos of wonderful nature and funny animals
Another place to go (which also is a great group-activity) is Taronga Zoo on the north side of the bridge. Just take the ferry over (presuming you're on the south side), enormous zoo with a great variety of animals and a fantastic view over Sydney Harbour! And of course the Syndey Tower on Pitt St. with a incredible view over Sydney!
Darling Harbour is also a nice place to go, with the Maritime Museum (I think..?) and the Aquarium (WARNING: You will probably be asked to take your picture at the entrance for you to buy at the exit.. with a Nikon..
).
Street photography is suitable almost anywhere on the streets of Sydney. Two interesting parts to visit (IMHO) is the chineese quarters (around the Haymarket) and the bohemian-ish Newtown, with interesting people and architecture.
While you're in the Haymarket area, it's not far to the Powerhouse Museum, which is a great museum for all ages!
And IF you guys have the time to go to Melbourne (skip Canberra... really..!) you should visit Michaels at the cnr Elizabeth and Lonsdale! Good camera shop, and with over 3000 (I believe) different cameras and lenses on display at their up-stairs camera museum! A must!
Well, there are a thousand million billion trillion (you get the point) other places to see around the Sydney-area, like the Blue Mountains and the beaches, but I hope some of my thoughts are helping!
Have a nice trip!
/Johan