I'm going to give him the talk
Why do you think you need to give him the talk? Do you think it is just because of his age?
I think that's a personal question to ask.
While discussing sex with a family member going through puberty can be awkward, it's something that should be done so that person can become more responsible and not risk contracting an STD or getting someone pregnant. It's good to be open and frank with your family members so that they know can come to you with any problems that they experience, including ones about relationships.
I take this seriously and I don't think I have time for this. Let's talk about something else.
I am glad you are taking it seriously. That is really the most important thing is that you are involved.