That sounds almost like my situation, the only problem my dad has with me smoking weed is that it is illegal and if I get busted with pot that makes him look bad too. I would just say fuck it, go have fun. If they ask you can choose then if you want to tell them that you are still smoking but until then...
i recently told my mum (my dad already knew) and she was a bit weirded otu at first but she said as long as it doesnt interfere with school and i dont lie to her and im careful etc then i should just enjoy my youth ^^ lol