I think, personally, if you're catering to geeks, go ahead and call them geeks! The banner and the bags are geeky (in a good way, of course), so I say, run with it! You don't have to be all things to all people. Those who are confident enough in their geekiness to carry a geeky monster messenger bag won't mind being called out, they'll probably like it. I think it's good branding, personally.
Though I am not a geek, I am indeed a nerd, and I fully own the moniker, so I think I speak with the voice of experience.