hehe, didn't you get the memo? In a surprise raid Wednesday night, the Caymans declared full independence and attacked the EU via the Med, slipping past Gibraltar
in the dark. The EU capitulated early yesterday and surrendered, so your trip will now be entirely within the New Cayman Dominion until you clear out of the Med and get pretty much all the way up into Scotland
Which just leaves you to enquire with customs
& immigration there.
Seriously? Considering the mixed nature of your party and the structured ownership
of the boat, you might want to send a paper letter to the Scots and Italian authorities, along with some of the other ports
you plan to stop in, and get their formal written replies, which may well differ for the different citizenships aboard.