I think he would enjoy taking you while watching you going down on the other gir that way there would be no contact between him and her and yet he still gets the threesome.. and if that works out with out any problems and every one is comfortable you could try a full on threesome?

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Some people they like to go out dancing
and other peoples they have to work, just watch me now
And there's even some evil mothers, haha
well they're gonna tell you that everything is just dirt
You know that women never really faint and that villains always blink their eyes, ooohhh
And that, you know children are the only ones who blush
and that life is just to die

sweet jane the velvet underground