Can you snap a pic or two of the damaged logs and post here? Seeing the extent of the damage and how deep the dents & dings are will dictate kind of repair needed.
Some minor dents can be repaired with nothing more than water... moisture reintroduced into the recessed wood fibers causing them to swell back top their original position - prior to the impact... the moisture can be applied many ways... i.e. cutting a sponge to shape, attaching it on top of the dent and keeping it damp... after a few hours or days, the wood is back to normal shape.
One great feature of logs is that they have so dang many beautiful imperfections... bold grains, checks, knots diseased areas, and a host of other markings. For deep gouges on your logs, consider these ideas...
* Chisel and sand the rim of the gouge to blend with surrounding wood. The dent can be made to look like part of the history of the log.
* Make the dent bigger :-) Chisel it out and add some dramatic character to make it look like a natural imperfection.
* Patch it... If the dent is deep and unsightly, match the wood section's color/grain with another piece of wood and cut a "patch" large enough to cover the dent. Trace the patch over the dent and chisel out the log's damaged area - slightly smaller than the patch. "Fine tuning' this procedure with coarse sandpaper, chisels and some good old fashioned whittling. After you've shaped the patch with the saddle cut in the log, use a good exterior/waterproof glue (I.e. Gorilla Glue) and seat the patch. You'll want to either use finishing nails to hold the patch snugly, or brace with some kind of constant pressure.
Tom, some dents can also be filled with a wood repair substance and finished to blend with the surrounding area. I talked about a similar DIY repair on a log railing. Maybe thhis will give you some ideas.
There are many ways to skin this cat, these are just a few ideas I'd recommend...