Annie,
Are you married? If so you should discuss your fantisy
with with your spouse or partner. I am married and would be happy if
my girl wanted to do something like that but would want to know about
it first.
I have been to a swingers party before. If you are not
invited you will be seen as an outsider and not well received. Its
best if the hosts know you and can introduce you around to
brake the ice.
Good luck in your quest to enjoy the
nectur of the gods!