Dear Geist,
What is the plural of McDonald’s? Everything I try looks wrong, and online search results are far from unanimous.
Dear Camille,
There are places where even editors fear to tread. . . To avoid monstrosities such as “McDonald’ses,” the plural of McDonald’s is simply McDonald’s. It isn’t strictly to grammatical code, but in context it is clear, and readability is what matters. If possible, though, try rewording the passage.