<human>: Can you give me a shortened version of the text?

Hello everyone. I swear I'm not trying to brag here... though since I've never really tried this, part of me wants to! Mostly I want to know if this is even possible, and if it is, how to keep it from blowing up in my face. 

As the title suggests, I had a great first date with a girl. As it just so happens, while finishing the date at a coffee shop, a girl I have known for a while but could never arrange a day and time to meet, walks in. After I leave with my date, the other girl texts me. One thing led to another, she said "you're attractive!", and we basically set up a time to meet next week. FWIW, I had only talked to this girl online (OKCupid), so we had never seen each other in person. 

So... the date from last night has no idea about OKC girl. On the other hand, OKC girl understands I was on a first date last night. So one knows I'd be attempting to date two girls, the other doesn't. 

The questions: should I tell the first girl that I'm going out with OKC girl? Or is that a private thing that I have no obligation to share? The first girl wants to go out again tomorrow, so she at least likes me enough for a second date. I just don't want to string anybody along unfairly, if possible. In my "dating life" I've had plenty of struggles with dating one girl, let alone two. Any ideas/suggestions?
<bot>: Two girls want to go out with me, but only one knows about the other. Trying my best not to be a jerk.