I'm kind of a nerd, so I used a simple excel spreadsheet. I was able to get 6 on one sheet. I just put my name, Virgin Voyages, Valiant Lady, Cabin Number, Sailing Dates and both of our phone numbers.
(Here's where my true nerd comes in.) I printed them on red paper, cut them out, laminated them, and punched a hole in the top.
I'd probably use the current cabin number for now, and carry a Sharpie if you need to change it.