You might want to consider putting a video camera in the window aimed at where they are running over your lawn. If they do it again, at least you will have a video to prove they did it, then ask them to pay for the damages.
If they are good neighbors just inconsiderate, they will pay or help fix the damage they done. If they are not good neighbors and refuse to pay, then you could always take them to small claims court to recoup the damages, or call the police. If they act that way, they are not good neighbors and probably do not deserve to be treated that way, so just sue them. I'll bet that tops them from driving on your lawn
...Rich