The best deal would have most likely been an open jaw IAH-SYD/SIN-IAH, but that ship has departed so to say. One way award tickets cost 100k if you can get a saver rate, which is not easy and certainly not for that many tickets. The agent quoted you prem eco on miles with an upgrade to business which will most likely be a waitlist (else 100k business should have been available as well). Getting that many upgrades is just as difficult as getting that many award tickets. So confirming instantly to business will be a JN award ticket where the bottom is 200k p.P.

It is possible that the $800 is a straight up confirmable UG to Polaris, but this would be an unusually cheap price for this route.

kids needs to fly in the same cabin unless you shell out a fee for unaccompanied minors.