what should I do mommas?

My oldest son turned 17 on April 2nd, he had been talking about a girl that he liked from school before his birthday but shortly after they started dating. Turns out, this girl is 14 years old. Same age as my youngest daughter. She doesnt turn 15 until Sept of this year. I’m super worried because I know that my son has had sex before and its not that I dont trust him, I would just hate to see anything turn out badly.. I dont want to tell him he cannot see her but I dont like when they are alone, she dresses and acts rather promiscuously (not that its an issue) but I dont want either of them thinking its okay to have any sexual relations this young, especially for her age. I just dont know what to do. I’m worried and I dont want her mother to get the wrong idea and accuse my son of statutory rape. I dont want my son to do anything with her and I hardly believe he would wait 3 years to have sex with a girl who acts like she may be ready! I dont wanna be a bad mom by allowing the relationship but I dont want to be a bad mother by telling them they cant be together either. Any advice? It was different back in the day. A lot of older parents/grandparents are up to 10 years apart in age difference but these days I never know what could happen with an age gap while they are this young...