@Anna10110 The guests are contractually entitled to all of the home amenities fully functioning as advertised. If something goes wrong, they should have the option of a date change to advance their checkout date and refund the remaining nights. It sounds like you've made every reasonable effort to fix the A/C problem, but if the guests still seem disappointed with their stay, the best you can do is encourage them to move on.
A bad review may or may not happen; nothing you can really do about that. But if the guests were using A/C wastefully, that is worth mentioning in yours.