Are there pick-up lines for play dates?

So I was at Michaela's ballet class, watching Evan ham it up for the other parents, when I experienced something that I have only read about before. I was propositioned for a play date. Wikipedia says a play date is an arranged appointment for children to get together for a few hours to play. Don't get me wrong, my kids have had arranged play with friends, but with friends we already know. But this was a stranger. Somebody, who in my mind, thinks that my kids are so cool that she'd like to have her kids play with mine, in hopes that their coolness rubs off. Okay, so maybe that's not what she was thinking. Maybe she just wants to hang out with me. After all, I am quite a catch. I rush in to ballet class all hot and sweaty, 'cause I had to put holey tights on Michaela and put her tangly hair up in a bun, all while keeping Evan from tearing the place up. Then I proceed to play ringmaster to Evan, keeping him quiet (as if that is even possible) while keeping this tornado of energy confined to a 5x10 space with no toys. If we do bring toys, I then have to keep him from crashing the car/airplane/buzz lightyear/alien guy/monster truck into the wall/chair/other parent/sleeping baby. And I'm doing all this while watching the graceful Michaela Plié/Chassé/ Passé/Relevé/Sauté and smiling approvingly. This mom has a little boy the same age as Evan. He's so quiet, mild mannered and speaks with a normal level of volume. She has seen Evan in action for 3 weeks now. So she knows what she is in for. I am quite happy that we've been asked to play. Most of the time, when we're in public, I get the feeling other parents are looking at me like "OMG! Can't you control your kid?" Which isn't really true, right? They are probably just amused at his antics. Either way, Evan's antics have not scared away this mom. So we exchange numbers on little torn pieces of paper, but now I'm wondering what the rules are about calling for a play date. Are there rules like supposedly there are with dating? How many days do I wait to call? Who calls first? If she buys dinner do I have to sleep with her? Oh wait wrong rules. This is all new to me. I'm used to my kids playing with my friends' kids. If Evan does something embarrassing, hits or won't share, I just deal with it, without fear that they'll never call again. But this new situation has a risk of rejection. But I'll cross that bridge, if it comes. Until then I start thinking of the excuses I can make for Evan's behavior. Isn't that what parenting is all about?