slap it up in his face.... " yo dad I Smoke pot, I dont give a damn what you think coz your a cockhead anyway.."
just smoke. if you really wanan tell them, then just tell them but its not a big deal anyway, seeing that youve found shitlaods of weed from them and your dad does coke, then i wouldnt be too worreid. and come on man! if they saw you growing, i THINK, i have a tiny inkling somehow, that they JUST maaaaaybe MIGHT know??! haha happy smokin'