Firstly make sure you get people there in the right ratios . . .
MMF is key - FFF and MMM are both wrong
SC
Normally a large bottle of strong spirits is a good ice breaker . . . Just relax and have fun, there really is nothing to worry about!!
But the main DO is to talk to your partner and ask exactly what they want to get out of the experience and tell her what you want - that way there can be no confusion about what the boundaries are and no worries afterwards due to misunderstandings and jelousies etc . . .
SC