Say it likes its not a big deal at all. Don't be like...mom I have to tell you something both of you should sit down lol.......then your making a big deal out of it. Maybe in conversation talk about some sort of drug you knowwww they would despise you doing, and be like, this one girl (that you know somehow) I caught doing cocaine once it was so crazy ....then be like, I mean I have the odd joint every now and then but you would never catch me doing something like that. If they react poorly just compare the two..lmao.