Trying new things.

My friend recently invited me over to have some fun. We see each other a couple times a month so it's normal. This time he invited me over to have fun with another couple. I've never been with another girl although I am interested in experimenting... I don't think he gets that i need to know what her face looks like before I commit. And the other guy, well I don't know him either. I'm now curious about the experience I would get from it.  How do I tell him that it's the girls face that would ultimately make my decision.. And how do I have fun without having fun with the other guy? More so how do I tell him it? I have some morals and I don't want to be with another guy, especially a new one I don't know.