Personally, I would bite the bullet and load them into calibre and do the work there. But, I wouldn't removed them from calibre afterwards.
If you can access the device as a drive, you could use Sigil to edit the epub. This has an editor for the metadata.
Hmm, a search found EPUB Metadata Editor
. That looks like what you want. Beyond the fact that it exists, I don't know anything about it.