At least, I couldn't get it to work, and I happen to believe comments elsewhere that the insufficient power from the Lightning slot is the culprit.
If your CF card is not still in the camera, then believe the various posts that say that you need a powered CF slot. Downside (at least to me) is having to leave the camera turned on to power the CF slot so you can import images, draining the camera's battery. Upside (at least to me) is simplicity connect two cables and you're done. Plug that into your iPad mini, turn on the camera, and the Photo app should "just read" from the CF drive in the camera using the camera's power. Connect the standard USB connector to the Lightning to USB Camera Adapter ($29 from Apple). It connects the mini USB B-type socket in the camera to anything that can take a standard USB port (computer, etc). If your CF card is still in the camera, start with the USB cable that comes with the camera (IFC-500U, in the case of my 5D Mk III). Not saying there might not be better solutions, but these two worked for me with a minimum of muss and fuss.
I found two techniques that "just worked" for me.
#Apple compact flash reader how to
I spent some time digging around various sites trying to figure out how to import and edit RAW photos from my Canon 5D Mk III (with firmware version 1.3.4) to an iPad mini 4 (running iOS 10.3.2) - so I didn't have to lug around a laptop to edit RAW, create.