This does not make sense. Obtaining a Hawaii state ID requires a visit to a Driver Licensing Center with two proofs of residence. Your friend would need bank statements, lease, utility bill, etc... to prove their address (two of the documents shown at the bottom of this page). These are not documents a short-term visitor would hold. This process is meant for, well, residents of Hawaii, not temporary visitors. If he already holds a driver's license in another state, he'd likely have to surrender it, and then go through another hassle to reapply after his trip.
Trying to establish Hawaii residency for a couple weeks could also have tax implications, and the annoyance of having to file a Hawaii state tax return could well exceed the benefit of any discounts you obtain.
You're visiting for two weeks. That doesn't make you a Hawaii resident. Trying to claim otherwise is at the very least unethical, if not fraudulent.
I'd also consider HI Rev Stat § 286-131 (2017):
No person shall:
(5) Use a false or fictitious name in any application for a driver's license or knowingly make a false statement or knowingly conceal a material fact, or otherwise commit a fraud in any such application; or
The form you will have to sign to obtain a Hawaii driver's license requires you to provide a "HAWAII PRINCIPAL RESIDENCE ADDRESS." A hotel or rental for a two week vacation is not your principal residence address.