Will have to see 
If you really want to go through with it. I would say to possibly think again of the benefits of seeing a couple.
The biggest one will be the girl will be totally relaxed. You will have few pressures put upon you too. She may be prepared to try more stuff due to her other half in the room than with two and complete random strangers turning up.
Plus the boyfriend wont be really caring less if you are packed in the trowser department or not, or if you display nerves, or show you are not ron jeremy at giving sex. Another punter it will effectively be doing an unwritten competition to seemingly outdo the other person and him constantly judging you too the entire time.
And the other thing is there is discretionary worries of hooking up with another punter that do not exist if booking a girl and her partner.
And you also have concerns if they other guy just doesn't show up leaving you with possibly his bill and yours to the girl.