Your DH seems to want to enjoy the full trappings and status of the Alpha Male even though either through economic downturn or reduced earning ability he now doesn't earn enough to fly you all the style to which you have become accustomed.
Are they overnight flights each way?I guess it depends how long the flights are as well. We don't know if its US or NZ, and an 8 hr vs a 16 hr flight would be very different times to leave your DCs in economy on their own for.
If its not overnight on the way over then I can see absolutely no reason why you shouldn't all sit together in economy or if that's too much of a hardship for your pampered prince, then premium economy.
The way back is somewhat different if he is going to work the next day. I guess in that case I can understand why he would feel the need to have a pull out bed style seat rather than standard economy. Then you sit with the children in economy but on the strict understanding that this is purely a cost based rationale, not on a he is better than the rest of you because he has a busy important job reckoning.