Sounds like a nice trip!

You might want to clarify what program your 170,000 miles are with. From the info in your profile, I assume that it's Delta. But make this clear in order to get better help here.

In fact, if your miles are all with Delta, you might want to delete your post here and re-post it in the Delta forum (since Flyertalk rules prohibit posting the same question in two forums).

In any event, in terms of using your miles, you should book the first flight as soon as possible. And then, if you still have sufficient miles left over, book other award flights as the dates open up. Some airlines let you book awards a full year in advance, but more typically it's about 330 days. I believe it's about 330 for Delta, but I'm not certain.

If you have enough miles, I'd aim for the two of you flying business class from Brisbane (or somewhere else in Australia) to LA, since that will be you longest flight. Plus the service and seats on international business class are generally better than on a US carrier from LA to NYC (which is only about a five hour flight, so not the best investment for splurging on business class anyway).

You're smart to look into availability a year in advance, since it's by no means guaranteed and generally the further in advance you book award flights the better.