Damn, Trump is one lucky S.O.B.
Using credit cards to pay for affair expenses is not very smart.
The airline and the cruise lines would have required proof-of-identity such as a U.S. Passport or US Driver's License to book the tickets and board the cruise. So, plausible deniability will be impossible if the allegations are true.
I'm sure accepting gifts of financial value from a vendor, and failing to report them, violates state conflct-of-interest laws and regulations.
We'll need a jumbo-sized tub of popcorn for this ...