Good tips, thanks everybody.
I'm trying keep a relaxed attitude to it all and just take it as it comes. The other guy is a good friend but we have never been in this sort situation together before.
Two things come to mind. The first is that you will work out a comfort level regarding involvement with the other guy. Exploring and respecting his limits will happen pretty naturally.
In these situations I think it is also important try and get everyone feeling involved, and comfortably engaged. Sometimes you can have moments when you would rather take one of the participants off, and do your thing together. I try to make a real effort to make sure no one is feeling left out or less engaged. In a group it only takes a two or three people to take this inclusive approach, and the whole thing will work like magic.
If you find yourself drawn to one person then explore that together when you are alone with each other on another, or later, occasion. The point of the event is that you will all feel great sharing with each other.
Good luck! Don't forget to report back. :wink: