I think for 4 people, this is a great option. 4 people on a multi segment journey all on points will be a struggle to lock in due to availability.
If you really want to do the Business Class experience, then either (a) book return flights to Singapore in Business on your points accrual, the rest in Premium Economy or Economy in cash, or (b) book the Australia - Singapore leg in Premium Economy or Economy end then the final leg of Singapore to Australia in Business or First as a treat for the family at the end of the holiday and the balance of the flights pain in cash.
