I'm not quite sure what you're wanting that sentence to mean? 'Man' cannot be used to mean 'one' in sentences where you mean to say that "One [of the children] is not playing..." or similar, it's only used as an indefinite, impersonal pronoun, often in statements like "One should not...", "One does not...", "One could argue that...".
If you're thinking of the royal one, it wouldn't work even if we constructed some bizarre situation where Queen Elizabeth was visiting a zoo and trying to make it abundantly clear that she was not playing with the bear there, because that's not a manner in which we'd use 'man' in Norwegian.
This was a listening question and I mistook Man for Mann. I understand the concept of "One does not simply walk into Mordor" but you might say something like "Man walks upright, as compared with cats." Is there a way to say that in Norwegian that uses the English word "Man" in this way?
i don't think there's a difference in pronounciation between those two, except perhaps a prolonged "n" sound for mann?
Either way, by reading or listening to this text, you can tell that by saying "Man does not play with bears", it sounds a bit...caveman like. So " One does not play with bears" is the answer that sounds more correct. Depends on context, really.