I went a couple years ago and customs screening consisted of a cursory glance at my passport both entering the country and exiting. I cleared US customs in the airport in Aruba, where we checked our bags once to clear customs, then once again to get them on the plane.
I carried a Leatherman Wave all the time, it was kind of heavy in shorts, I wish I had brought my Victorinox One Hand Trekker instead. I also had 2 dive knives, 1 small one that was pretty crappy, and another double edged, dagger-style with a skeletonized handle that I carried from time to time. That particular knife has been to several places in the south pacific as well without so much as a hassle.
The people are pretty laid back in Aruba and very friendly. The police presence in the cruise port (Oranjestad IIRC) consists mostly of bicycle mounted patrols by pairs of officers.
FWIW I don't think you will have much of a problem with a small knife like the Flash, but personally I would choose something that isn't assisted to take with you to avoid confusion with a "switchblade."
If you are going by cruise ship, you may have a little more difficulty with the knife.
Pete
