Honestly I think you should tell your aunt in person. I know where you're coming from. Saying it out loud makes it real in a way. And it makes sense. It should make it real. But when I told my closest friend I did it in person and out loud (at work of all places too!) and as terrified as I was I just HAD to say it out loud. She had a good reaction, too. She just hugged me. I hadn't thought she would react like that though.
As far as family, I think you should for sure do it I person. Then you can look them in the eyes and they'll know you're serious. Personally, I don't trust Facebook. People say a lot they don't mean on there. But in person...it makes a difference and like I said it makes it real - not just for you but for who you're coming out to, too.
Just my thoughts. ~