Here's something to think about. It can be equally fun for the boys or the girls so let your imagination guide you.
You stop by my house, maybe to see if I want to go to lunch with you. The front door is unlocked and you step inside. You hear what sound like giggles and muffled sounds coming from the bedroom. When you investigate you find me on my bed tied and gagged, (use your imagination at this point as far as how I'm tied, gagged and if I'm at all dressed). With me is a girl friend you also know (also you decide how she is dressed if at all). She is "playing with me" and on the floor is a duffle bag with a supply of rope, bandannas, tape, and different toys. I'm obviously enjoying what is being done to me as much as she is enjoying what she's doing to me. When we both see you, I start making efforts to get my friend to turn me loose so I can explain, as my friend starts trying to offer a stuttering explanation of her own.
How would you handle this unexpected show?
Would you simply tell my friend to continue and watch the show?
Would you join in by offering to tie her up and gag her. Either on the bed next to me or tie us together. Then "playing" with both of us, using the toys you find in the bag?
Can't wait to see your ideas.