If you only have 7-days and you want to really see hawaii, then NCL's Pride of Hawaii is probably the best option. You fly to Honolulu and board the ship, and then every day you are in port, staying overnight in Maui and the Big Island (Hilo one night and Kona the next).
There are three ships, but Pride of Hawaii is the newest and the nicest, and this is its last year in service in hawaii (they are moving it to Europe).
I see prices as low as $399/week on all three NCL ships in Hawaii, or $899 per person with airfare included. That is a very good deal.