You should be fine. Air Tahiti Nui's fare codes for award tickets are:
A = First Class
Z = Business Class
Q = Economy
If you are really worried about it, call Air Tahiti Nui directly. They'll reconfirm your itinerary for you and since you are traveling in a premium cabin will take your seat assignment request as well. You can find their contact information at:
http://www.airtahitinui-usa.com/company/offices.asp
Good Luck!