Please help I really Need advice

My 3 year olds dad recently got off probation and I think hes smokeing marijuana now that hes off probation should I confront him about it or just stop letting her go over there???
My mom used to smoke and I know others won’t admit they do but idk if I should make a big deal about it or not I’m just really confused and worried cause i dont know if he will relapse on the harder drugs cause of this and I know he will think I’m just being spiteful and wanting to start dramma by bringing this up

It’s just pot. Its not a huge deal as long as he can still function.