Actually, I have some good news - I copied about 100 or so wallet files to a flash drive, and copied those to an old PC that was hanging around.
I found that not only does the tool properly decrypt all of the files, but it also does what I was hoping. If you decrypt the wallet files a second or third time, it does *not* overwrite the decrypted file (or the file restored from backup already), and instead decrypts them and renames the file with (1) appended to the end of the file, and if you do it again, it will do (2), etc.
Example is if "Test.pdf" has already been restored from backup (or already decrypted), and if you run the tool to decrypt the wallet file again, it will decrypt the file again and rename the one you just decrypted to be "Test(1).pdf." So it looks like I am in good shape!