A Roman palace you can live inside, and a ferry terminal to a dozen islands.
This is a shape, not a schedule. Each day has two anchors and a lot of slack, because 3-day itineraries that book four things a day fall apart the first time lunch runs long. Move things around freely — the neighbourhoods are grouped so that walking between stops actually works.
Island-hopping with a group is where plans quietly fall apart: ferries are limited, they sell out, and one missed sailing costs a day. Put every departure time on one shared itinerary and give the ferry bookings to a single person.