Well it's been about 2 years since our black lab passed away. She was a handful for quite a few years but never did swallow rocks. However she used to dig up bulbs and eat them much to wife's consternation. She used to dig a hole next to the cedar bushes to get shade in summer. She used to eat her own frozen poop.
That was just a few things she did. As mentioned above labs need exercise - walking, running and of course they love swimming. They really need to be tired out so they don't do silly things like swallow rocks etc.
Distractions needed are chew toys - kong toys, rawhide chew bones. As it has been mentioned before dogs are permanent two year olds. Get your kids more involved with the dog. I miss my black lab but don't miss the trouble she used to get into. So lately have been dogless.
G.