A child that young that sticks everything in it's mouth is never left unsupervised anyway, or at least shouldn't be. I have never heard of dogs eating anything other than grass. But i'm not a vet, i guess some dogs do.
When I sold my home in San Jose 6 years ago, it was full of potentially toxic or poisonous plants, oleander, brugmansia, etc. I raised my children and grandchildren there, had numerous pets over the years, not one, child or pet, ever ate a thing in the garden. The new owners, a non-gardening couple with their first baby, proceeded to tear out all kinds of wonderful mature plants, because grandma said they were poisonous. As a first child, I doubt they would ever let him unsupervised so to me, it was unnecessary. But to each their own I guess, for their own piece of mind.