Non-religion? Why would atheism not be an appropriate descriptor in this situation? (I'm honestly curious.)
A religion is a system of beliefs regarding life (Why are we here?, How did we come to exit?, etc). Atheism is not a religion, it is merely rejecting the belief in a deity. It does not attempt to answer any other questions.
As an example, agnosticism is another non-religion that is distinctly different from atheism.