You've spent hundreds of dollars for costumes and classes already. Travel to the event is another big expense you wish you didn't have. Island hopping to get to the different Heiva (Tahitian dance festival) on different islands can sometimes (who am I kidding? all the time) be expensive, especially in Hawaii. Why not pool your frequent flyer miles together to get airline tickets? A great way to rack up the miles is ask friends and family to donate to your account. Many airlines now allow sharing miles. Get 5 friends to donate 1000 miles each and you are almost there for a one-way inter island flight (usually 7500 miles one-way).
Another way is to use a business credit card that gets miles. They usually have annual fees but if you use it enough (spend more than $500 a year) you'll usually be able to justify the cost and savings toward a flight. A word of caution, these credit cards usually have higher interest rates but if you keep the balances down or at $0, this won't be a problem. If you haven't started yet, you should and you'll be that much further ahead next time you need to fly (outer islands or the mainland).
Hawaiian Airlines has several credit cards/debit cards that get miles through Bank of Hawaii. And don't forget the partner retailers and special offers (for example, Foodland occasionally offers double miles redemption for their shopper rewards program). There are some partners that offer 5x miles the dollar amount spent. But timing is key on these offers. One way to make sure you are at least aware of these offers is to sign up for email alerts or add their rss feed to your favorite news reader.
American Express Rewards is also a great option. If you can collect enough points for flights, you'll be able to save quite a bit. If you don't have enough, try looking into hotel accommodations and/or car rentals as another way to cut costs. You can also link frequent guest accounts to accumulate points faster.
What if you have a large group? Check into chartering a flight. Many times large groups are attractive to carriers as it guarantees seats, dates and revenue. Group rates are generally lower that then standard retail rate too. A total package is worth looking into so ask about that as well. Travel industry professionals always have information about deals, promotions and additional rates that hotels and transportation might not publish to the public. It doesn't hurt to ask. If you can get it all in one place, it makes it that much easier. That way you don't have to keep constantly following up with all aspects (but make sure you do some follow up no matter what).
Lastly, a no-brainer, make sure you add your frequent flyer number to your flights. Flying to the mainland and back will get you about half way towards an inter island award flight. Make sure all who are flying are getting miles. Sometimes I forget to add the number to my kids flights. (they get miles too as long as they have a paid seat). If you forget, you can add them in retroactively too as long as you do it within the required time (Hawaiian Airlines gives you 4 months from the actual flight date).