I'm in pretty much the same situation as you, started HRT, laser, etc. and living in another city (about an hour away, so not quite as far as you) but still living a double life is hard.
I'm not quite as far as you into transition but I know it will be months before I feel ready to come out so it's only going to get more urgent, I think a email/letter is the best way to approach difficult parents, give them time to process it without all the emotion getting in the way.
I always feel like I would be a wreck if I tried to explain it to them face to face and probably wouldn't handle it, I'm not sure, maybe I won't. But at least with an email/letter, I can put a history and all the little details I might miss out in a face to face.
I don't think it's cowardly, at the end of the day you still have to face the music regardless of HOW you come out. And I would be much more reassured to then talk to someone ONCE I know they are going to be civilized and want to talk about it, rather than be irrational.
Including a picture is a great idea, I think if they see how successful your transition and how much happier you are it will be easier to accept (this is one of the main reasons I'm waiting).
Good luck hun, I hope it goes well for you!