Hi Luise,
With the dates you've given I think its very unlikely you'll be able to visit Perth Obs. I do volunteer work there and know the night tours are over by then. But to make sure ring! during office hours to make sure. Things have been a bit shaken up there at present so best not to get your hopes up, sorry.
As for observing opportunities, check the
ASWA calendar - there is a lunar night on while you're town. Not too far to drive and always a social night.