Right. As I pointed out, roundworms are in ordinary soil everywhere, in fact the most common way dogs pick up fresh infestations is walking on dirt then licking their feet. (Tho a dog on a meat-based diet will have a gut water balance and immune response that keeps ascarids at a very low level; also, there is some evidence that a low population of "normal" parasites are *required* for truly sound intestinal balance. Which a lot of breeders had already noticed, since 100%-parasite-free puppies tend to have more issues with unexplained diarrhea.)
Right. The odd lump here and there from reasonably healthy critters (or dead critters from natural causes) won't hurt anything and will provide concentrated nitrogen. But this is different from trying to make compost from materials that are *primarily* poop (or corpses :) In nature, poop gets dropped here and there, is a very tiny minority of the total, and is worked upon by all the stuff around it. It's not piled all in one big heap. (Tho Garden Cat is making the attempt... she's got two distinct *piles* going in my side yard -- not that it's going to hurt the desert sand much.)
BTW, some years ago someone did some research on why certain swaths of Europe, most notably in Germany and France, have such spectacularly lush growth, above and beyond what is typical for the region. A glance at historical maps, and some digging, made the reason obvious: these are areas that have been battlegrounds for centuries, and have a rather high concentration of, um, composted corpses (blood is a wonderful fertilizer!) and rusted armour.
And there is somewhat more risk in over-protecting a child from their environment anyway, as the immune system *requires* a certain level of challenges to develop proper and normal immunity to the ordinary gunk of Real Life. Frex, it's been discovered that kids who grow up around dogs and cats have a much lower incidence of allergies as adults, because their immune systems got a useful level of challenge for developing to best performance and least chance of overreaction (allergy being essentially an immune overreaction). Eating a bit of healthy garden dirt now and then isn't going to hurt a kid, in fact it's far more likely to be good for 'em.
~REZ~