Lets assume that genies grant wishes literally, but will twist your words. How do you wish without unintended consequences? Typical rules of no more wishes, no resurrection, no forced love, no altering the past, can’t defy logic, can’t break physical laws, can’t create paradoxes, and can’t affect higher powers (this is one tough genie!).
(And it was either that or replacing the water they drink with milk and making them lactose intolerant, but that would use two wishes)