Oh you’re so lucky to be going to Hawaii. I’m jealous! My advice, as a Hawaiian is to stay put. It takes a few days to slow down to Hawaii speed- for me it sometimes takes 2 weeks to get back in the groove. I recommend going out to Hana, see the sacred pools, hike to twin falls, go to little makenna for a sunday drum circle, walk the streets of lahaina, chill out as much as possible. Lots of tourists make the mistake of island hopping to see as much as possible and in the process really miss Hawaii.
That said, however, you can fly interisland- there are no boats beucase the channels are too rough. The major airlines Hawaiian and Aloha have fares for about $50 ow in advance but can go up to $100 ow last minute. There are some smaller airplanes that go- Makulele I think?
As for islands that can be visited quickly… that’s such a hard question. It depends on what you like to do on vacation. Kauaii is incredibly beautiful and romantic. Big Island has more interesting things for kids- like snow and an active volcano. Oahu has all the TV hawaii spots for surfing and shopping and the smaller islands are more private and romantic as well.
Have a great time- aloha nui loa!

Well any international airport. Kauai is out of Lihue and Maui has another international airport (forget the name). Both islands have private airports as well if you are able to afford it and charter boats (boats were hard to research, but locals said its about the same to fly).
My recommendation for island hopping is to check the inter-island specials on Hawaiian Airlines or other airlines. We got ours for $29 each way.
As far as which island to see its all personal preference. Kauai is the most isolated of the tourist islands, not much to do and activities are expensive (well every island is expensive). We personally like Maui, super laid back, people are nice, no rain, more swimmable waters spots, and towns to see.
Oahu is Maui x 3. Same thing, just a city vibe and TONS more people.
It all depends what your intentions are, i.e. sitting around and doing nothing, hiking, activities, dining, or sun bathing. Good luck and have fun.

I would try to go to Oahu..Honolulu is a great city..i went to hawaii for the first time 3 years ago.. and i LOVED it… it is the coolest place you will ever go…the sunsets are amazing… Not sure how much it would cost to go island hopping though.. Have Fun!!