Likelihood of getting 3 seats to SYD from DFW/LAX/SFO during X-mas week next month?

I am DFW based and thinking of non-revving (ZED) to SYD on QF/DL/UA preferably on QF from DFW along with my 2 children. I heard the loads from DFW are pretty high. So I am thinking of LAX. I am pretty much flexible to leave anytime after December 19 but have to return by January 1st after spending 2 days in SYD and 2 days in gold coast.

Will I be able to make it or risky? Not much experience in non-revving to Australia. Any advise is appreciated.