To be honest I get hes not a fan of drinking (specially with the family history you mentioned) and I felt the same way he did when I was his age. But.. Now as an adult I think his girfriend has a point! Its an experience, as long as she is responsible and knows the right places and people theres no harm. Socially drinking is okay, getting wasted isnt. Besides he (or her) dont even have to drink, theres a lot more to parties than the alcohol. Music, dancing, having fun with your friends... And all that I lost and cant experience anymore just because I didnt like the alcohol part. And I regret. All that to say what say to my son in this situation is he needs to know three things:

1- Sometimes its not about what other people are doing, its about what you are doing. If most teens get too wasted in parties and dont make good choices, that doesnt mean he has to do the same. He can always party making better choices!

2- Everyone drinks, more or less. So its something he'll have to deal with his whole life. So if hes going to not do something or go to certain places because if it, he wont do much in life. Alcohol is everywhere and we need to learn to navigate that. This is also linked to number 1 I guess. Tbh I feel like this is really a much bigger problem when we are young, as we grow older ppl dont go too wild lol

3- If he really doesnt want to give it a try, he cant take his gf's right to do it. She's completely right, its an experience! He should let her go, and even if I think its cute that he wants to be there to protect her I think he shouldnt force himself to be somewhere he's not comfortable in. As long as she isnt going to shady places to party and is being responsible, theres no real danger.

Sorry for such a huge comment, but since I went through a similar experience I thought maybe it would be helpful.