Though I might not be able to relate to you completely, I do know where you're coming from. Believe it or not, I live with my grandmother as well, and she's none too happy about my transition. She constantly tries to talk me out of it, telling me that what I'm doing is overly drastic, and that I'm 'addicted' to my sex-change. Yes, she considers my transition an addiction. I've tried to tell her that I don't care what anyone calls it, because it happens to be making me happy, but I just can't get her to see it my way. I don't expect her to, but I wish that she could.
Unlike you, my father is actually on the same wavelength as my grandmother ( It's his mom, so I'm not surprised that they see it the same way, ) Only, instead of calling it an 'addiction,' he calls it my 'experiment,' He often asks how I 'know' that this will make me happy, and I've told him, "I don't know if it'll make me happy, I can't predict the future, however, I do know that if I don't try something to make me happy with who I am, then I'll always regret it - at least, if I try it this way, then I'll know that I've done everything that I could," He tends to think that if I don't get surgery, that I can go back. He doesn't realize that my voice will never be the same, or that clitoral growth exists xD Regardless, he's just plain not happy about it and won't talk about it unless I bring it up. He also refuses to use a gender neutral pronoun or try to use the right one.
And then...there is my mother. She's extremely supportive. She tries to learn about the LGBTQ community for my sake. She uses my chosen name. She tries to use the correct pronoun while talking to me, and she introduces me as her transexual son ( I wish that she'd just say her son, instead of her transexual son, but it confuses the general public without the trans in front of it since I don't pass as a guy yet, )
Anyway...unfortunately, I don't know how to make it go any smoother with your family. Some people will understand and accept it right away, others might need some time, and some of them will never accept it. You could try educating a little bit, carefully try and get them to talk about it with you a little more - but try not to cram it down their throats.