"....it's going to be an even bigger mess in a year or two when the rebar goes through a few cycles of shrinking and expanding,"

Where I live the winter temps are near zero and the summer up to 90 degrees F. That is a shriking and expanding problem but yet the concrete surface lasts 10+ years. And I would not think that the small temperature changes on the island would cause the problem you describe. Now maybe with shoddy construction practices and poor materials (like extra sand and less concrete/gravel)....