One thing that would concern me about bringing an older pet of any sort to Hawaii, particularly one with possible existing health problems, is the quarantine requirements. Hawaii is a rabies-free zone and thus has these requirements where the rest of the US does not.
While there is a 5-day-or-less quarantine option, if you have not done the proper preparations to qualify for that option well in advance, the quarantine in Hawaii is 120 days. That is not something I'd want to subject an older pet to.
Hawaii Animal Quarantine Information