Just back from 2 weeks in Acklins. DIY trip all walking (up to 8 miles a day)
I bought a pair of Cabelas flats sneakers for the trip. They're lighter than my Chotas and held up really well. A lot of the hikes were over coral and limestone , no problems.
I bought them 1 size larger than I normally wear. I did get a little chafing around the collar of the boot, but not bad. I wore high socks and folded the tops over the top of the boots, that seemed to keep out most of the sand. Perhaps you might want to cement over the vents.
Hope this helps.