You seem to be stuck on the idea of using point to Asia but like somebody else suggested, try using using points from Asia to Europe.
The advantage of that is in that you know what you are spending in Au $ as opposed to have to deal with currency conversions. The other advantage is that you have more choice of partner airlines from Asia to Europe than you have out of Australia.
Another way to do this is to buy a one way ticket to Europe on points and one way from Europe back home for money, or the other way around. Most one way fares between Australia and Europe will allow a stopover in Asia, if this is where you want to stop to break the journey. As to which of these combinations is teh best, that could be down to luck and availability.
Apart from accounting for currency conversion and seasionality between certain destinations, there is no much science that you could apply to your decision.
One website that I personally find an absolute blessing for reserachign airfares on multiple carriers, is kayak.com. You can filter search results by alliance, by number of stops, one way versus return yourney, or even multi city journeys. You can ask for a quote to be given in the currency of your choice but be warned, this is just a search feature - the actual charge will be in the currency used by the retailer/ airline that sells you the flights. Anyway, have a little play and you may find a combination of flights that normally wouldn't have stood out as the most obvious one.
On the point of availability of reward flights, I am sure you know that QFF only shows some partner airlines using online search engine, yet for others, e.g. CX, you would have to call their call centre to find out, and if you decided to book it, would cost you additional points/ money to compensate for their service.
Finally, when seraching availability of rewards flighst online, cometimes it pays off to literally ask for a combination of flights that would take you through a transit port, a hub of that partner carrier. E.g. in my experience, I needed a flight from HKG to LHR and wasn't able to find one by enetering these two cities in the origin and destination. As I didn't care for a direct flight, I then searched for HKG-HEL and HEL-LHR, and was able to get both on AY. Another time, this same yourney was offered to me as HKG-HEL-LHR by the search engine.
There are reasons for why this happens as I work in the airline industry but it's going to take me too long to explain; basically, it's about individual carriers maximising their revenue between certain markets. The important thing for you to know is that sometimes you won't be offered the reward seats becaise they are not available but because you didn't 'ask' for them in a particular way. It's all about trial and erroe, and most importantly about persistance. If all fails, in the travelling party of 2A and 2C, it is feasible, at leats in my opinion, to fly 1A + 1C using one solution and the other 1A + 1C using another solution. You can time your arrival to be in the same spot at the same time and still enjoy the holidays as a family.
How you get there is mostly irrelevant, so long as it safe, reasonably priced and comfortable.
Hope I was of some assistance to you ...
