I'm a Gold Qantas FF with sitting on over 1 million points. I've tried to buy 4 J seats to the US for January 09 using points but with no luck (as usual).
From my experience, phoning QF and getting a helpful telephone agent is the best start. It's a million times easier for them to check availability and suggest different routes than it is for you to try each and every option using the QF website.
The few times I've redeemed by FF points for First / Business international flights over those peak periods I've had to book as far in advance as possible but if you're looking for this December that's probably not very helpful.
As others have suggested, be as flexible as possible with your routing to maximise your chances of getting to your preferred destination - remember that QF flies to the US from Sydney, Melbourne and Brisbane (and possibly others also that I don't know about) so don't limit yourself to one particular departure city. Also be willing to split up into groups of 2 and to fly on different carriers / routes to get where you are going, as it is obviously much harder to book larger groups using points.
Depending on how much time you have you might also consider doing an around-the-world redemption and starting your trip by flying to the UK / Europe. FF flights to the UK seem to be a bit easier to obtain, and you have more choice with the airline which again helps with availibility.
Once in the UK it should be relatively easy to get a LHR-JFK or similar flight for your whole party - I've got a BA flight booked on Boxing Day this year in which we have 6 F award seats and 2 F upgrades from DONE4 fares. By the time you are ready to return from the US (assuming that's going to be Feb 09) you should have slightly improved availability on the pacific flights home.
Don't forget either that in a month or so you should have the ability to redeem your FF points on any seat rather than just the FF award category seats, so your large points balance will come in handy there.
