I had them in the lawn of the house where we used to live and couldn't identify them so carefully removed them in case the dogs were attracted to them. Fairy rings often form where a tree or shrub has been removed and aren't specific to one type of fungus, so I think they're best removed or fenced off just to be on the safe side.
I also keep a close eye on William and Louis on our New Forest walks from late summer and through autumn because of the huge number and variety of fungi/toadstools. I've never seen them show any interest yet, but I know that some toadstools, like the bright red, white spotted Fly Agaric, are poisonous. Those are easy to identify but lots of the others aren't.