Hey there,
I can say I've had exactly the same thoughts and feelings before starting my transition, and the very same concerns about transitioning as you.
Being young, hormones will help you out a great deal if and when you decide to go through with it. They're not going to turn you into a beatiful woman, but they're gonna lend you a strong hand.
Just about every one of us is concerned with passing, but with a bit of effort put into makeup, hair and other things, one can easily pass. It just takes time and practice.
Transitioning does take time, though there are people who present as female even before HRT, some it after a few months, others after a couple of years. I'm planning on going as female for the first time after around 10 months, because I know I'll feel comfortable to do it then. My hair will have grown out, I'll be moving to uni dorms, etc, and I'm sure I'll be able to pass, even though I consider myself masculine and ugly. Which brings me to the next point.
We all want to be pretty, cute, beautiful, sexy, though it's not how it works. There are quite a few things one can do to make themselves prettier. But eventually it comes down to your genetics. Some people are pretty, some aren't. Beauty is in the eye of the beholder.
As far as your family goes, I don't think you should be concerned with them. If they love you, they'll accept you (possibly after a while) and the most important thing in your life should be your personal happiness, not anyone else's. I personally didn't want to wake up one day, 40-ish years old, deciding to go through transition and dragging possible children and wife through it. Very many have done so, and I admire every single one of them, because for most it has been hell.
In conclusion, it would be best to see a gender therapist and tell him / her of your issues. If you're already determined and have set your path, seek an endocrinologist to start out with HRT. I advise you to tell your most accepting family member about your issues, as well, as soon as possible.
Good luck and take care.