It depends on the Temp, forecast is 25max at Omeo and 14max on Hotham. Elders is a great site. http://www.eldersweather.com.au/vic/alp ... alls-creek
During this years Audax I had Arm warmers, short fingers and a wind break but the forecast was a bit warmer. There sounds like a few rest stops this year so carry more gear than food. I can't under stand rider packing for a 3 day ride and carry to much gear. I recommend Arm and leg warmers, wind break and a jacket if rain is predicted.
I did the ride in 11 hours and I was about the 20% mark of the field so there was many riders after me. Average was 13+Hours for 250Km so many riders will finish in the dark.
In terms of lights I would recommend the best you have. There are no street lights(don't laugh - some rider last year didn't have any lights) and it's very dark with some little down hill sections in the last 20km. Some rider had to walk these or closely follow someone with ample lighting. Don't forget a tail light.
Enjoy the ride