I will be traveling to Hawaii in the future. I've heard that taking NAFs to humid places such as Hawaii & Florida present some issues. Not clear if this is true or what I should take into consideration.
e.g. take an inexpensive bamboo flute in case it gets damaged....or take a harder wood etc.

Any thoughts?

A lot depends upon how different your climate is from the one you are traveling to. If you live in a cool, dry place (where your flute have happily resided for some time) and you go someplace hot and humid, it can potentially cause problems.

It all depends upon the flute (how it is finished, what it is made of, type of glue, etc.). Most softwoods won't have much trouble because they don't have very stong grain tension. Some hardwoods, however, can really react to temperature and humidity changes, and the most likely result of a severe reaction would be compromise of the glue seam.

I've only had that happen twice, when flutes I made from very hard woods traveled from my cool, coastal climate (North coast of California) to hot places during the summer. One went to Phoenix and one went to Atlanta, and both had some separation at the glue seam. It was fixable, but a sad nuisance for all.

However, this is unusual. I've shipped lots of flutes to hot climates with no trouble at all. If you keep your flutes out of the weather (indoors) or mostly in their bags or cases and out of the sun, I'd be surprised if you had any trouble. Keep the flutes waxed. Don't be shy about contacting the makers and asking them for advice as well.

To add my personal exerience, I've travelled to Maui with one of Geoffrey's Redwood flutes (F#) and had no problems. I had it in a soft padded cloth carrying case.

Last December I took 5 flutes with me to Taos. The weather there was around freezing during the day and dropped into the low teens at night. I played during the day and at night with the flutes as cold as the ambient temps at time. No problems. Again, the Redwood from Geoffrey. A Lacewood flute from Ed Kort. A Purple Heart flute from Ed Kort. Another flute from Ed, I think it was Maple. And a Sassafras high C from Colyn as well. All survived just fine.