religion as a word is rooted to the 12th century and at the time the meaning was more of a "conciece awareness of the greater influences to which we are tied to". it wasn't until around the 18th century that the word morphed into what you are defining it as today. i prefer the older definition in part because i want to qualify athiest as a religion because i view it as my religion.
the non-religious are the ones that are not conscientious of the "bigger picture". of those that are conscientious, most believe in some sort of a god. some, as i do, don't believe in an external influence such as god and only believe in the world as i see it now. some don't know which belief, if any, is true.
my point is only this: there is a huge distiction between not giving religion any thought and giving religion thought and coming to the conclusion that there is no god.
Well, if we don't want to be debating semantics on an internet forum, it would be better for all if we stuck with the more familiar meaning of words and how the huge amount of people understands them.
I believe you will only be causing yourself a problem when mixing atheism as your 'religion'. I say this because then you will be viewed as the person with the positive claim that there are no gods and therefore you will have the burden of proof on this one. On the otherhand if you say you are (for example) a secular humanist and a rationalist, then you would probably still be stating your 'religious' view of the reality and atheism would simply be a consequence of your rationalistic view. Therefore when someone would ask you to prove a god doesn't exist, you can reply 'define your god and I will tell you if I believe in it or not'.
to make it simple, simply saying you're an atheist is meaningless. to be an atheist you need to be in respect to a certain claim that someone will put (like YHWH created the world in 7 days and heaven exists somewhere in the sky) and then you can be an atheist to that god claim.
(i hope i could explain myself well, sorry if i didn't)