You can get around the problem of the questionable arity of "nobody" by using an alternative phrase like "none of us", which is explicitly singular.
"None of us is important" is probably the most grammatically correct rendering of the idea, but it's not a perfect semantic match to the original sentence(s).
"None of us is anyone important" is a bit better of a semantic match, but it's awkward.
"We each are nobody important" is the best semantic match, but nobody would ever actually say that.
Ultimately though the original sentences were not about none of the people present being important, but instead the fact that it was not important for the second person to know who anyone in the first group of people is. Therefore to match the intent of the original sentences, I would probably say something like "It's not important for you to know the identity of any of us."