If there is availability on NW from any location (MSP, SEA or DTW) to Hawaii, then another alternative is that you can use either CO or DL to get to the Hawaii flight. In other words you can mix and match segments.

We are doing that next March. In order to get what we wanted, we are flying
Houston to LA on Continental,
LA to Honolulu on Delta,
Honolulu to Minneapolis on Northwest,
Minneapolis to Houston on Delta

Weird but we got what we needed on the date we wanted.

Also the availability can change day by day so I suggest checking online frequently and then snap it up if what you want appears.