Hi,

We have made the return flight twice with two kids (12 months and three years).

The first time we didn't have a stopover and this was a nightmare for everyone when we got to Oz for about a week.
The second time we had a three day stopover in Malaysia. Although there was still some restlessness on the flight everyone had adjusted a little to the time difference and we were all well rested.
So I'd definately recommend a stopover.
Hope this helps.