I have read through your post three times now and have come to the following conclusions:
1. You may be going the day after you come back

2. Your itinerary and associated sub-plots have been written by Miss Marple.
3. You may end up with four flights but no cruise, two cruises and no flights, a quick turn-around shopping trip in Italy or none of the above.
4. This will stand you in good stead for the "Veridian Room" type of quest in the future.
Good luck with your cryptic cruise!
