I've come out to my best friends via letter but I really don't want to make a big deal out of coming out to anyone else because I hate attention, so do you think it would be a bad idea to just slip it in the conversation "oh and by the way I'm non-binary?" I think I could do that but I honestly can't just say it to someone as if it's really important.
Hmm... It might be best to have a subtle lead up to it. Maybe steer the conversation in that direction, if possible. I think you have a good plan though. Don't do what makes you feel uncomfortable.