I must say, that this thread has been a fantastic record of the construction of the reefer. It really looks fantastic down there on the waterfront!
Stewart, the displays sound great. To answer your question on the QR Codes- since they are just a binary representation of text, they are unique to the given task/URL. By using a QR code generator (there are a few on the internet), it will output a downloadable image, that simply can be used in whatever context you want. I don't believe that there's any need to register anything, and there is thus, also no cost. My computer isn't currently cooperating, so I can't get the download to work. But I would do a search for QR Code Generator, and assuming the downloaded output is indeed an image file of the QR code, you could just drop it in with the information being put inside the reefer already. The whole process seems pretty simple from what I can tell, and I think it makes your idea to put codes up around the museum for "off hours" visitors, an excellent one.
In effort of full disclosure, I have almost no experience with actually using them, as my phone is not that "smart" (ha!). But I've read a little about them, and have a friend who answered many of the same questions for me awhile ago. But I hope this helps out some.