The first thing you need to do is change your departure port to Los Angeles as from Miami you would need to travel through the Panama canal to get to the Pacific and then onto Hawaii. To my knowledge there are no cruise lines that do this. Princess do 14 night roundtrips to Hawaii from LA with 4 islands and also Ensenada. There are 9 days at sea in total so go prepared. Alternatively you could fly to Hawaii and use NCL on a 7 night itinerary which only calls at the islands so you get much more time there. The best time to go is thiw time of year. If you go, you wil love it. Hawaii has some fascinating and beautiful places to visit. It's worth the travelling.