I think they should stay the HELL out of the bike lanes, but there's not much more you can do about it. You can always yell a bit as you go by. Or maybe look up the laws/rules of the bike path, and have cards printed and hand them out. Kind of a friendly crusade.

Yes, asphault is softer than concrete, but compare to our legs and soft-cushioned running shoes, it is not worth taking into consideration. I have a jogger buddy at work, and he runs on gravel trails. These are notably softer than concrete. So is grass. If you're that concerned about the impact on your legs and back, you probably shouldn't be jogging in the first place.