Chuck, Keep in mind the ship will not have the services of a bank or pursers desk for check cashing like on a regular ship. They will accept the travellers checks for payment of things like onboard purchases and bar doubloons (another story for another day).
The security thing in the room is not what you think it might be. Keep in minfd the size and close contact nature of the ship. Where would someone go with stuff from your room?
I suggest your get a water proof "wallet". Leave most of the stuff you might normally carry in your wallet and pocket home. Bring one, maybe two credit cards, license (for ID)
medical insurance card and leave the rest at home. We carried mostly cash and I usually had it on me in my water wallet (plastic container) either around my neck or in a pocket (I wear swimsuit with pocket that zippers shut).
I have read Windjammer message boards for several years and never read a post about an onboard theft.