critique my travel plan please

[kuri77]

A buddy and I were planning to motorcycle in Australia from Jan 1 to Feb 15 next year. The tentative plan is to go up from Sydney down the coast to a friend's house in Melbourne, down through Tasmania, then back up through the interior via Alice Springs, Darwin, Cairns (taking in national parks in the general area) then back down the coast to Sydney. We could do that in reverse since nothing is nailed down yet.
It all sounded good temperature-wise since I knew "our winter, your summer" but I'm starting to check Oz weather daily and it looks like it may be a little too early since it appears to be raining everywhere, in the north especially. Would putting it off a month till Feb1 to Mar15 be a better idea? We can live with some lower temps but don't want to spend most of the time in our rain suits.
First visit so don't assume I know anything other than in this post. Am going to get a guide book for some ideas but would like input from people who have maybe done a similar route or live along it. If you have alternate route suggestions great but we are on vacation so not planning on any day over 250 miles. We want to look around a lot and take pics not do an Iron Butt. So anything, maybe parallel to the roads I mentioned or a short cut or long cut, that is more interesting we're all for.
As you see from the map it's about an 12,000 km trip which will give us about 300 kms a day which is around perfect for our style of cruising.