Partner going to child’s frat/dad weekend?

How would you feel about the idea of this? Our son’s frat is apparently hosting dads for the weekend. It supposedly involves some organized activities including a golf outing. But also a party with a sorority. I am so uncomfortable with the idea of my partner being out amongst college kids surrounded with alcohol etc and also a bunch of college aged girls. I’m not sure if that mixer would include dads of the sorority girls or their moms. If it’s their moms, all the weirder. If I say I’m uncomfortable or no he will accuse me of not getting over it and still holding his past against him. I have horrible pictures in my mind of him sneaking off with some 21 year old or her mom. Our kids don’t know about online and phone sex betrayals (that’s what I know of and unsure if he has lied about real life physical encounters). I feel bad bc my kid is the one who misses out if I push back on this.