Should a person in committed relationship vacation without significant other but with single friends?

My BF & I dating for 3 yrs. We have traveled alot together &had the best times.We both enjoyed being together vs. not being together 95% of the time. Recently his VERY single friend asked him to attend a wedding for a guyfriend in FL.I have overheard them being typical boys about hitting beaches-partying w/the bridesmaids,(jokingly, as this is how his friend is most of the time in front of me or not,they dont know the brides maids to be honest)My issue is that out of nowhere,my BF agrees to vacation w/single friend over Memorial Day Wkend& to me this open doors &compromising situations where I know his friend will encourage his old "wingman" to play while the cat (me)is away.I have turndown many trips like this w/my single gfriends because of this reason as I valued our relationship more than a good &possibly carefree time.I cant help but to feel betrade inside & his decision has made me loose sleep.I come family of cheaters, am I allowing my past tocontrol me or r my concerns valid?