Hey Tascha,
I have not cruised to Alaska, but several of my friends have, since it's so cheap to go from here. I have heard it's great to go in late spring because it's getting warm then. I have heard the ships up there are AMAZING and the tours are really fun. Some friends and I have talked about going on one in a few years.
As for Hawaii, I'll play the part of resident Maui expert.
I have been to the island four times (including getting married there) and have been to Kauai once, on my honeymoon. I absolutely LOVE Maui because it has both the nature (i.e. the road to Hana, the volcano, which has an amazing sunset bike ride option) and the more "touristy" activities (i.e. parasailing, whale watching, snorkeling, shopping, etc.), unlike some of the other islands. I have not been to Oahu, but it's a lot more urban -- flying into Honolulu for a layover to Maui, I was surprised there were high-rise buildings -- and Kauai is SUPER outdoorsy. It is gorgeous, though. Maui is really the best of both worlds, and Kaanapali Beach has been voted one of the most beautiful beaches in the world.
I have been to Hawaii at different points of the year, and while the weather is absolutely perfect around the end of June, I'd suggest going in April or the beginning of May. It's still going to be great weather and warm enough to swim (unlike February, which is more warm than hot and July and August, which are burn-your-feet-on-the-sand hot) but it's also low season. Hotels, airfare and rental cars are cheaper during low season (technically April through November) and then they skyrocket in mid-May.
Hope that helps! If you decide to go to Maui or Kauai and want some recs, let me know! (And maybe you'll run into us! We're debating when this spring we're going to Maui!)
