Personally I don't think that big of a trip regardless of it being a drive or flight is suitable for a newborn bub. Its so tiring for them to be lugged around everywhere. I'm not trying to start a debate, just my honest opinion.

BUT if you HAVE to go, I would seek the ok from a medical professional that a baby that young can handle a plane trip. Not just the word from others who have done it. I would opt to fly over drive because a baby that young will sleep alot in the car & you could risk missing feeds because baby is asleep so why stop to feed just yet. So you would run the risk of baby becoming dehydrated, your milk supply suffering etc.
How long do you plan to be in Taz? what are you doing there, visiting family or seeing the sights?

Can the trip be put off till bubs is a bit older?

It would depend on who you fly with I guess & what "class" your ticket is for but virgin & jetstar only have the seatbelt thingy that was mentioned above. No extra seat for baby under 2 yrs. You hold them.
Also my last experience on a plane was with a 1 yr old. it was a 3 hour flight & was with virgin. I was sat right up the back, so my seat didn't recline at all, I had no over head compartment because those ones were for staff so all of my baby bits where a few seats down. I was right near the toilet so I was BFing & would have someone basically leaning against the side of my seat while waiting for the toilet to become free. the reason I was sat there was because I had a baby (under2) & it was near the baby change toilet.

If your going to fly with a young bub, make it more comfortable & pay for a decent "class", trust me.