The document requirements for cruise shore excursions changed today; how can I proactively mitigate booking risks?

When confirming cruise shore excursions for a client today, the supplier updated the document requirements, and some non-U.S. passport holders now need additional documentation. The sales page hasn't been updated yet, so if they booked directly, they might be denied boarding on the day of the excursion. I first cross-referenced the excursion requirements against the guest nationality list one by…