I'm surprised people think August is feminine! Never heard that, but different takes on names are interesting.
I have never met a girl with the name August, only heard rumors of them existing (although usually the reference is vague, so not much in terms of confirmed actually people!) Seems like an odd girl name to me because I don't see it as gender nuetral at all (it means KING afterall). That said, be warned: if you name a child after a king, expect him to act like one
So, those are my warnings -- it is not a name without complications
Also, people do like the nicknames Gus and Auggie, and we like them also actually, but by three my son wholly rejected such names and insists only on being called by his full name!