The advantage of Digikam is that you can actually geotag non tagged images, or modify the geotag if it’s off, using the map directly in Digikam.
But to come back to what the OP wanted, Digikam and ART make for a great combination for geotagging images when the camera has no GPS, and ART exports the GPS coordinates to the exif data in the exported jpegs, and those can be used later on in a blog, but I don’t know if it can de done for wordpress.