The bottom picture isn't very clear, but I'd check to make sure that isn't Giant Hogsweed before I went anywhere near it.
But I can't figure out if Giant Hogsweed is actually poisonous, whether to humans or animals. It's terribly invasive and causes horrid blisters, and that's that.
But I sometimes toss "baby" plants into the chicken run of what I think is Giant Hogsweed (there's an infestation in the corner of the property which needs to be cleared). And so far there seems to be no issues. But we're talking sprouts under 2" here, and usually toxins are less concentrated in young plants. So I'm still unsure about how edible/inedible it is to creatures without exposed epidermis.
But yeah, I'd find someone local to ID. Learning about all the plants that call your yard home can be fun, but I think it's especially important if you keep animals in it.