Very excited to see this thread as I travel to Hawaii every winter for at least a month to visit my family. I am an O'ahu native now residing in Upstate NY, which is why it is crucial I bypass at least some of the winter each year. I try to make my home visits a productive ones and regret to say I have not tapped into the local permaculture networks as much as I'd like to, but I know there are lots of them. I would love to help make this voyage a reality, and be involved.
I would suggest getting in touch with Waihuena Farm:
http://waihuenafarm.com/ - They host a great deal of permaculture events and may be able to help with accommodations, although January would be peak season on the North Shore of Oahu (where I grew up). I know them through my father who has ties to the family through a solar business they run. Best to get in touch with Meleana. I could also share contact info if you guys are really serious.
Transition Oahu could be helpful as well:
http://www.transitionoahu.org/oahu-permaculture-design-course---winter-2014.html
I would also like to echo Keahi Maumauma's comments and agree that all who plan to visit should definitely "Do [their] homework." It is helpful to have an understanding of Hawaiian history before visiting as most peoples' knowledge of it is very (tactfully) limited. I avoid pineapple for what it represents. Not saying you should too, but educate yourself before indulging. Also, it is definitely in your best interest to stay with locals. I know if I'm in Hawaii during January, I can at least promise a huge Hawaiian feast with my family, who love hosting guests (Kaneohe, HI).
I am surprised that no one has suggested visiting Moloka'i. For me, it is a very powerful place that I respect greatly. There is a lot to learn from it and its people; important activists and teachers reside there. Not to mention, the community is most welcoming. Geoff Lawton has showcased quite a bit of what is being done there, including restoration of fish ponds and other tours of pockets of permaculture. I visited Moloka'i High School last year and they have a nice permaculture landscape in the works, with the help of students (my uncle is a teacher there and introduced me). I enjoy this interview with Hawaiian activist and educator, Walter Ritte,
https://www.youtube.com/watch?v=n61pLhJjXdc. You can fly from Honolulu to Moloka'i for ~$100 RT.
http://www.mokuleleairlines.com/
One thing I want to point out is -- I know there are a lot of transplants who practice permaculture that you will easily connect with, but I hope you all will make it a priority to connect with natives who have carried on these systems for generations. There is a lot to learn. Take the time to work in a lo'i (taro patch), help restore a fish pond (
http://paepaeoheeia.org/getinvolved/)... then reward yourself with pineapple.
Looking forward to hearing more about this.