Oh my - you little Spazzmanian Devil you
No - I'm not going there, you know better.
Anywho, regardless of what happens or not between two adults is where it should stay.
You are not a mean person for saying NO. At the same time, you are not a bad person for having sexual fears, doubts, curiosities, adventure and so-on. You would hardly be human if you didn't.
What concerns me about the situation here, is that after all the planning and time spent prior to the actual visit, this comes up now.
Seeing the writing on the wall / reading between the lines are abilities obtained through experience alone. Perhaps this can be a good learning experience for you regardless of what happens. I really doubt anyone will like you more or less one way or the other. But people are concerned with your future safety and well-being, regardless of the fun we try to poke at you. Thing is, if we knew you didn't enjoy it, we wouldn't bother.
Just a side-note, the Haven might be a more proper setting for such truly sensitive concerns.