I thought it was somewhat incongruous that Michael would ask Fredo to show Senator Geary et al a good time in Cuba knowing that Fredo had never been to Cuba before.
Additionally, I thought Fredo learned the list of "local" drinks a little too quickly for a first visit. Perhaps that should have made Michael suspicious.
"Generosity. That was my first mistake." "Experience must be our only guide; reason may mislead us." "Instagram is Twitter for people who can't read."