you lucky bastard
id let your girl set it up if i was in your shoes get them round for a few drink or whatever im not experianced in the multiple girls at one time part of pick up yet still trying to get good on lone girls at the moment but my advice is
dont mention the four way or anything sexual over text as the girls might have been down for it at the time but there minds change real quick when they leave and bringing it up could put them off meeting up with you guys again
what id do is give her number to your girl and let your girl do the work arrange some kind of night out plan the night out before hand so you have a solid way to get back your place
and if these girls are is down as you say they are things should take care of themself to get your 4 way once back at your place
like i said im not experienced enough to give proper advice on how to take care of this when back at yours but you and your girl sound like you guys did a pretty good job the first time so i think once you get them there you guys will handle the situation