You should start the "talk" out like this...Look, Mum, dad...uhhhh I have something serious to talk to you about. For like, several years now I have been smoking crack and snorting coc off of prostitutes. After they sh** their pants, you can then tell them that you smoke weed and that you really don't smoke crack or snort coc off of prostitute's asses. Then...it won't be so bad. I don't see how this couldn't work