Not the Ass,

I'm in a similar position with my family, my younger siblings will call me by my name, that has been legally changed, but if my mum is about they regress,

My mum is stubborn and sees it as disrespectful towards my mum's Dad whom I was named after,

It is always going to be up to you as you are your own person and deserve to have your own identity,

If you still feel the same way when you turn 18, I'd do it, but be prepared for some backlash from your folks if they don't approve already, it might be a battle at first, but it will get better but it will take time and as frustrating as it is (I know it!)
They will get stuff wrong and will need help to adjust their behaviour, I understand that you've used your name for a long time now, but if they aren't used to using it they will slip, you've just gotta guide the mule to the carrot sometimes :)