So, if I understand correctly, you intend to go out with people you've known for years, drink and socialize, and have sex with one of the guys you've known for about 15 years. Did this friend tell you he wanted to have sex with you when he texted? Or are you hoping he wants to have sex with you based on what he texted?
Friends with benefits is a type of relationship. One night stands are too. I'm not a fan of mixing casual one night stands with long established friendships. What if he's bad in bed? Or worse, really good in bed and you want too much relationship too fast?

You're an adult and you get to make your own choices. If a one night stand is what you want, maybe your pool of friends isn't the best place to find one. Would you make a kayaking group out of people you had casual sex with?

I hope you make the best choice for yourself and a healthy healing process.