My teenager plans on having sex tonight. Do I stop him?

l have a son and he’s just 17. He has a girIfriend, she’s 18. She’s a grade above him- she’II be a college freshman and he’II be a senior. His girlfriend is having a graduation get-together at her family’s cottage for graduating seniors and junior friends to say bye to their graduating friends and it starts in about an hour. About 20 minutes ago l overheard my son tell his friend that they’re having sex this night. He said he had condoms and he plans on making it romantic with candles. I don’t know what was said after that because my husband called for me. I was going to confront my son but I really didn’t know what to say. He’s a bit still mad at me for something I did months ago and is just now speaking to me again. So I think I have to hand this over to his dad. Should we prevent him from going out tonight? I just think this will be a mistake because he's just a kid..