The cruise is a quick one, and only offers a couple of extra-fee shore excursions, both during the Mykonos stop. For my money, I'd choose the Delos island excursion over the walking tour of Mykonos, since the latter you can easily manage by yourself if you wish. Gate 1: 11 Day Greece with 3 Day Cruise and Airfare
Note the phrasing - that three-day cruise is included in the 11-day total, not in addition to it. Gate 1 also counts your travel days, which is acceptable since the airfare is included as part of the trip, but my personal philosophy is that flight days are never quite the same thing as a true vacation day.

