For the absolute best safety I would transit via Warwick, over the great divide to Boonah and then down into the Lismore Valley.
Anywhere north near Armidale all the way through to just south of Warwick is very high country and you need to cross over a lot of tiger country with very few landing opportunities to get to the coast.
This would be my recommendation for an inland route, for a more scenic flight coastal go Cowra to Mudgee, Mudgee through to the north of Newcastle, probably through the valley at Gloucester and then up the coast to Byron.
You will have controlled airspace at Coffs Harbour but they always let recreational aircraft through provided you have a working radio and transponder. Tyagarah is a great airfield but it is a little bit rough at the moment, Ballina is completely security controlled. Perhaps go there one direction and back the other.