As mentioned by drck1000, multiple day courses especially that go for 3+ days are not easy for those who are new to shooting as in beginner style courses. Many are not physically prepared and mentally there is a lot to take in. The mental aspect, especially when working with firearms for beginners is almost as exhausting to their body physically as it is being on their feet and in the sun for multiple days. I do multiple day courses on a regular basis (most recently for 11 days in April) and even though I am used to it, it is still tiring. 4 days straight for many is not pleasant. I teach multiple day courses on a regular basis and just instructing I am feeling it after a week straight and I have a 2 weeker coming up the end of the month.
From pure logistics standpoint of holding courses here in Hawaii, it is challenging. I know many of the big names on the training circuit and I am continually asked about civilian or open enrollment courses in Hawaii as many trainers would love to come here. Start explaining range difficulties and overall logistics and things get complicated and costly quickly. Oahu is obviously your best bet as far as student base, but range situation is complicated. Private ranges like the Big Island is great, but that includes a lot of money for travel as many students will be from Oahu. Not knocking the Big Island in any way as I love it there and I am with family up in the Mountain View / Glenwood area often enough and shoot over there, but it can be darn cold and very very rainy especially in the winter months. While hard core types would push on, basic level courses and their students are definitely not benefited from those conditions and the overall experience might not be pleasant especially after factoring in costs to get there, etc...
I know Travis Haley well enough, from back when he used to live in Hawaii pre Magpul. When he left we stayed in contact and once he hooked up with Magpul he always wanted to hold courses here but he understood the issues here in Hawaii first hand. It would be great to have training courses here in Hawaii and I really hope you guys can get it done. I wish logistics and politics were less complicated.