I've got a few irons in the fire and it's starting to become a little stressful.

Now, anybody with half a brain knows that when you're juggling multiple interests, you never ever allow the interests to meet, talk to each other, be in the same room. All that can ever happen is bad.

And it seems to me that two interests I've been juggling might meet this weekend and I'm going to try to do everything in my power to pre-emptively control the damage. So here's the situation:

There are two girls that I have VASTLY different dynamics with.

Girl A: I've known this girl for basically my whole life. I've been friends with her longer than anybody else. Very recently, like a month ago, we got drunk and had sex. Now, don't get me wrong, it was some great sex, but we both agreed that we weren't looking for anything more. I mean, I wouldn't call her my fuck buddy because of how long we've known each other, but I also would never call her my girlfriend.

And then there's Girl B: My relationship with Girl B is almost completely the opposite. I've only met her recently and am in the process of "courting" her. See, she's more of the old fashioned type. That is, she's not very big on the casual sex. I have to prove my worth to her and earn my reward, which I'm fine with. Who doesn't like a good chase? So I've taken her out on a few dates and spent some time with her, although I haven't seen much action out of her now, I think she'll be worth the investment in time.

Now, the beauty of this is that both of these girls do not live in my immediate area. So I can see them when I want and do my own thing when I don't.

The problem I'm having right now is both girls want to come in this weekend to see me. And I already told girl A that she could visit at least two weeks ago, and she lives much further away so she'll be staying with me the entirety of the weekend. Girl B, it seems, has decided to also come to where I live to hang out. Now, Girl B is also friends with a lot of my other friends, so she doesn't need to specifically hang out with me while she's in town.

The problem here is that it is my friend's birthday tomorrow and there will probably be a party and both girls will probably be there. I was thinking of briefing girl A, the old friend, on the situation and letting her know not to blow up my spot. I'm honestly not sure how girl B would react if she found out about the other girls, since we're not exclusively dating one another or anything and she's not really giving me any incentive to stick with only her. However, I know she'll be less inclined to have sex with me if she finds out that I'm a dirty manwhore.

Sorry for the wall of text.

TL;DR: Juggling two girls, wondering if I should brief one of them so she knows not to blow up my spot.