I came out in grade 11 to my friend, and then by the time I graduated all my close friends and family knew. Personally, I'm so glad I did; even with just one close friend knowing, it gave me an outlet to vent my frustration, and someone to be real around. During the first two years of High School, I was pretty depressed, negative, and introverted, but as soon as I started telling my loved ones (those are the only ones that HAVE to know; only tell people that you care about, because those are the only ones that matter (the whole "those who matter don't mind, and those who mind, don't matter" type thing), I became instantly, SO much happier, and so much more social and extroverted, it was amazing. But, this is coming from the perspective of a gay man, as opposed to a gay woman, and our family situations sounds different; my family is very accepting and loving, and you sound like you're doubting your family's acceptance.
I suggest thinking it out in your head, what you value most at the moment; Is it your self appreciation and self acceptance, or your close ties to and acceptance from your family. It's a personal decision, so don't let anyone push you in either direction; think it over, and do what you feel deep down, is best

Best of luck.