The answers to flying questions there don't appear to helpful. I haven't flown around there for years but did quite some years ago, but would think flying in a twin IFR would invite potential problems with icing. It can be quite savage if you are in visible moisture.
If you are essentially a sight seeing trip why bother with that extra problem especially if you aren't current and have negligible IFR time. I flew around there in C180's, Austers (par t of it glider towing) a debonair and various Cessnas. All VFR with no problems.It can be quite spectacular on a good day.
Keep in mind standing mountain wave. Gliders soar in up to 20,000 ft and more so although our "Snowy Mountains" are relatively low in elevation compared to overseas mountains, they do have a good "wave" system. The upper parts of the wave are quite smooth but anything below the main wave (and in the rotor area) can have a very rough and unpredictable ride and in quite clear air. Lower levels, say below about 10-12 thousand in a strong westerly which is common in winter can be quite rough. Cooma (YCOM) can also have a very decent crosswind in those same conditions from memory.
If you can, maybe have a talk to the tug drivers associated with Canberra Gliding Club.
All that said, it is generally not much a problem flying around there and just requires the normal common sense.