you may want to consider stopping in California (LAX or SFO) for a day to acclimatize the three hour time change and then finish off the trip. I look at travel to NZ as just being 3 hours behind west coast time, not 21 hours ahead and I'm okay.
Maybe I'm doing my maths wrong, so correct me.
seattle 8 pm
anchorange 7 pm
honolulu/papeete 6 pm
auckland 5 pm the next day because you have crossed the dateline
Granted, I did the trip in Business class after a loong week in NYC and Paris, we still didn't have any problems w/jetlag.
Good luck, it is an amazing country. I would go back in a heartbeat, even in coach.
lala