I don't believe that pushing the Sydney departure back by a couple of hours would work. As it is, I believe the flight gets into Sydney about 7.30 p.m. and turns around the same night and departs at 9.30 p.m. back to Honolulu.
You have to remember that Sydney has a curfew from 11 p.m. to 6 am., so pushing the departure from Honolulu back by a couple of hours would likely mean they would not be able to turn around the same night.
We have done the 2 week vacation to Oz via Honolulu with the stopover. It is not ideal, however the good thing is you can connect to the mainland on the same day you come into Honolulu from Sydney.
We go to Oz 2-3 times a year. Our urgency to get their determines the routing. Over the last year we have gone via HNL to SYD on Hawaiian, via HKG on Cathay and from SFO on Qantas. What I like about the Hawaiian flight is even though you lose a day with the stopover I actually feel better when I arrive because it is only a 10 hour flight and it is nice to arrive in the evening, clear a nearly empty airport and hit the bed shortly after.