Aloha Air connects Las Vegas to Hawaii via Oakland, CA. (One flight a day, I think) I doubt the cruise lines use Aloha (don't know for sure).
California to Hawaii can be more like a 5-hour flight if strong headwinds. Return trip can be 4 hours.
Hawaii does not have daylight savings time. So between April & October the Aloha state is 6 hours behind NY. So breaking it up could help adjust. Of course, that assumes you can sleep in Vegas if you choose Vegas!
Major airlines have red eye flights out of Hawaii....you leave late evening and arrive in California at like 5am. You can connect to 6am flights to NY (~ 2:30pm arrival), but you'd have to be a complete masochist or really short on time to do that.
Last spring Celebrity had great deals on airfare. A buddy of mine paid $100 for air from San Fran to Honolulu and San Diego to San Fran.
Sadly, simply, Europe is closer to NY than Ny is to Hawaii!