The advice above is very good. I have just a few thoughts.

Regarding lions: Scotland is part of Britain, so a "British" lion would not be unwelcome. And yes, the lion rampant has been the royal flag of Scotland for several centuries and is a commonly-seen symbol of the country.

The shirt and bow tie you wear with your tuxedo will work fine with the Prince Charlie or black Argyle. Your tuxedo shoes will also probably work fine.

I lean towards fur for formal sporrans, but no one is likely to fault you for a smart leather model with a metal cantle.

As noted, it's best to avoid white hose. Although traditionalists may prefer argyle or diced hose for evening formal wear, no one will criticize you for wearing a solid color if you prefer. Don't be afraid to try a bolder color (claret, yellow), as it will likely look better than black.

Skip the fly plaid.

I hope you are able to set sail and have a great cruise.

Andrew