I'm a tad confused.

You say in your post you will have 270k in US miles available for the trip which means you "could" do 3 UA 90k awards - but in the same sentence you say "but we'd also have to pay to get to NZ" - apart from the taxes on those 3 tickets, I'm confused about why you would have to pay more.

You're also including Qantas in the deliberations. I understand that you are including them because they are currently a US redemption partner - however QF is well known for making availability difficult to come by in the premium cabins. Getting 3 award seats on QF would be... significantly difficult.

Since UA no longer flies to AKL under its own steam (who knows what might happen by May 2005 though) you'd currently be looking at a Star Alliance award, using US/UA to LAX/SFO and then NZ to/from AKL.

I do not think you would have problems getting from CLT to LAX/SFO but getting availability on NZ will be the issue. If you were flying later this year I'd suggest trying via SFO as that's a new flight and perhaps may have better award availability, however the route may not last so I'd be a little hesitant in using SFO for long range planning at this stage.

I also think you were asking is it better to purchase business class tickets for 2 of you and redeem the 3rd as an award ticket? Well that's an option and likely easier to find 1 award seat on your flight of choice. However you are planning significantly far enough out (and May is not fully peak season) that you may just get those award seats.

Hope this helps somewhat.