Women: an above-the-knee hem is appropriate, or an evening pantsuit. Flat shoes are entirely a-ok! Men: suit, tie optional.
Crisp! It's the middle of winter, so bring a warm jacket for outdoors, and make sure to have a cardigan or suit jacket for indoors. Also: http://www.bom.gov.au/tas/forecasts/hobart.shtml
Click the RSVP link and enter your name - You'll be able to view all events you'll need to attend, and add them to your calendar.