"date" sounds like marriage to me. and lots of pressure too. expectations abound when you start talking about dates and taking out.
imho, i wouldnt really care if the valkarie sister from hellvalla tagged along. so she might have an afc bf wannabe, so what. you're the dj, you're the man in this situation. you gotta be the one with the balls to do what you want and to get what you want. in the end i think what you need to do, is get her to want to go out with you alone - get her to be the one to make that decision. it shouldnt matter if her whole family is there to watch you woo and seduce her with your dj kung foo, it shouldnt change anything about how you do your thing. you've only got your girl to worry about, and if you've got your own social gravity/charm by being C&F, then you'll befriend the girl's sycho-sister and her afc man.
i think it might be a good idea to try and take the pressure off of the date by realizing you're just hanging out, trying to have a good time - you're not trying to impress anyone, not trying to be anything you're not. just you and your girl having a good time. everything else can just revolve around you.
when they realize you're trying to have genuine fun and they buy that you're not only after shoplifing the pooty, im sure they'll calm down.
i think double "dates" (ugh) work out better when you go out with someone you know thats also on the path to dj enlightenment. in general, i try to avoid wordage like "date", "dating", "seeing" coz it can easily come back to burn you when you're committed to someone, unless youre not. i find it much easier and socially flexible to invite girls to do things you'd normally do, they can join you and you are the star of the show in that case - its much more low key and under the radar.
when you say date, you imply that you're trying to impress the girl, that you're willing to allow her to evaluate you as a mate. that you're probably willing to pay her way through the night etc. in the end you basically dont really get anything out of it except the right to try and impress a girl.
2 cents