I'd only ever heard 'chinned' to mean to punch somebody - specifically an uppercut to the chin, hence the name; but I suppose it might equally be seen as an extension of chinwag i.e. a conversation, and a heated one at that.
Context is everything here. If they were pleasant, friendly neighbours, who had asked - and who believed in give and take, doing favours for you as well - then I'd have no problem at all in their driving across the drive when it was vacant. In fact, I'd probably suggest that they do it (although I'd probably use the lower half myself occasionally or ask visitors to use it, just to avoid any future claims of rights of access).
However, they're clearly some of life's takers, who think that if you aren't using (or haven't secured) your own property/possessions, they're fair game for anybody to help themselves. Leaving concrete on your drive is massively disrespectful - vandalism, in fact.
They're no better than animals, really, who will find and take food, unless you keep it safe from them; but they don't know any better - humans (over the age of 3) do.