Photos Imported From Camera Change File Names

First a little back story;

I've been an avid photographer for twenty years, and I have a library of approximately 60,000 images. In self defense, I've organized them using the default file names assigned by my DSLR. I'm not about to try to change that.

I've been using a PowerBook as (among other things) a portable storage/ transfer device when I'm away from home. Alas, the beloved PowerBook has developed the motherboard-only-sees-one-memory-slot problem that's been an issue with these since day one. :-( It was time for a replacement. After considerable research and looking at what my (non-photographer) friends have, I decided on a 64gb iPad Mini for Christmas. I bought the dongle camera attachment kit, and I can transfer my images from my camera or memory card to the iPad and save them there or upload to my MacPro. Great stuff! ... Except the iPad apparently replaces the default file name assigned by my DSLR with a time and date. :-(

This WILL NOT DO at all!

How can I preserve or recover the file name assigned by my DLSR?

Without the ability to preserve file names, this iPad is nearly useless for the function I purchased it to do.