Oh nonononononono bro, you bring the wife into this fucking first step. Before you even namedrop the kid in his audible range you fucking get your wife on board.
If the two of you are divided on this, that's gonna be even more problems.
You need to get the wife on the up and up that the kid's doing it, it's done, and Hell-- maybe the condoms were an impulse thing and all he's done is like, touch her panties gently. Lord knows I didn't get any action at fucking 15, I wouldn't have known how to get it, and I was a shy introvert with awkwardness on-board.
You should try and appeal to your wife's care for the boy and tell her this is the opportunity like no other to set him on the right path and make sure once and for all he has sexual education befitting a man of his age. The birds and the bees, yanno? (I never got the metaphor teebeeach) But your wife needs to know that he's not an enemy in this, he's not 'acting out' or trying to chafe you guys or nothin' bad, he's just exploring life. Tentatively, carefully and safely, in an age where it's retard-easy to do the exact opposite without even realizing you're doing it.
No, I'd recommend very highly that you get your wife first, and make sure she understands your level on this. You also don't want to try and preempt her only to learn she's preempted you, or something, you know? You two need to be a unified body, because he-said-she-said is one game a parent really can't afford to play.
I repeat: you, as a unified parental unit, need to express to your son the proper way about sex, conduct regarding contraception, all those fun things-- but mostly that he can go to BOTH of you. None of this, "dad's not home but mom's a humongous bitch about my sitch so I'm not gonna start her bitchin' in this kitchen"-- he needs to know you are both patently his team leaders, his mentors, his sensei-tachi.
Thank you for putting up with my windy-ass posts