I'm heading to Mexico for my cruise this year, but last year I did a week-long cruise in Hawaii and really enjoyed it.
If you live somewhere cold and rainy/snowy, winter can be a fantastic time to escape to the Hawaiian Islands, and a cruise is a great way to do it. Usually when you visit Hawaii, you spend all your time on one island, but a cruise lets you visit four or five different ports (we did four separate islands on my NCL cruise) and see some of the less frequently traveled spots.
For fewer crowds, book your cruise when the kids are in school (avoid Thanksgiving and Christmas/New Year's Eve when prices are higher and ports are more crowded).
This Hawaii Cruise FAQ can answer some of your questions on cruising the Hawaiian Islands, or you're already set to go, you can visit Travelocity to check rates on last minute cruises:
Search by Cruise Destination on Travelocity