Should I be selfish or selfless in this situation?

I am an incoming freshman attending CSULB and will be commuting from home and I am going out with an incoming senior in high school. I really do like him and he will be gone for 2 months over the summer, so it got me thinking. Senior year for me was amazing. I want him to experience all of it and just have a good time as I did, but I feel like he can't have that if he's with me. I know how he is at school dances. He hooks up with girls and goes to parties all the time. This is the first time in a long time since he's settled down and had a legitimate girlfriend. I'm being selfless in a way that I want him to have fun and do whatever he wants senior year. If he wants to hook up with some random chick, go for it. But if he wants to do that, I don't want him to be in a relationship with me. At the same time, I'm selfish because I want to be with me. I really really like him and I want to think that I'm enough for him. I asked his friends for their opinions and they said that it's up to him, but he's been hooking up and all that for years, so maybe him finally getting a girlfriend means he's ready to stop and settle down for a while. I don't know what to do. I just don't want to tie him down. I want him to have the full experience of senior year, yet I want to be with him. I can't be with him if he wants to be carefree during senior year and do whatever he wants, which includes hook ups. I refuse to get cheated on. I would never cheat on him, so I expect the same in return. I don't know what I should do. Break up with him now [he's on the other side of the country for 2 months] and just be carefree over summer break, or stay with him ignoring the risk factor of me tying him down?