Two batches.

"Ok, I'll make two batches." It's more work, but you don't really mind. The sun is shining, the air is just the right blend of warm and cool, and you don't have a care in the world right now.
You make the weak margaritas first. Half the tequila and triple sec you would use for a normal margarita means that they'll be pretty tart, so you pour in a little simple syrup to sweeten them up.
You pour out the slushy concoction into a pitcher. There's enough for 4 or 5 small margs in that one. Should keep the illegals satisfied. Then you make the proper margaritas for the full grown adults, a little stronger than normal. You'd like to get to Margaritaville as soon as possible.
Suddenly, you curse inwardly. You don't remember which strength is in which pitcher. Before you can do a taste test, Riley runs up and pours two clear solo cups full of the frozen goodness for her and Alli. "Thanks daddy!"
"Ri-" but she's off, handing the drink to her cousin and sucking hers down. You taste the pitcher she poured from... God damn it. Sure enough, it was the stronger one. And those were big cups.
Oh well. Just...don't let them drink too much, you guess.
Karen stands next to you, having walked over while you were blending. "So...which is which?"
You just shake your head and pour them all together into one big one.
"I fucked it up, so I guess it's all good." She shakes her head at you.
"You had...one job, Jameson. Oh well." She sucks back a margarita of her own. Then she starts pulling at your shirt. "You gonna get in the pool, James?" {if KarenSFantasy = 1} It's very easy to take her playful tone and behavior the wrong way. At least, you hope you're taking it the wrong way. Karen has been a flirt as long as you've known her, and it hasn't diminished with age. As her sister's husband, you're a "safe" target, that she can play her games with and not worry about what might happen. {else} Her tone is playful; she's always been a good mother, a hard worker, but she cuts loose when its down time.{endif}
"No, Karen." Your phone and wallet are sitting on the coffee table inside, but still, you don't let her bring you close to the pool. "I shouldn't goof around while Jenna's inside, working hard. That wouldn't be fair, huh?"
You continue setting up the bar, and have a few margaritas yourself. You're feeling pretty fine in no time.
At one point, you find yourself dangling your feet in the water, watching Karen swim the length of the pool. Her body really is quite something, especially when it's moving through the water. Out of the corner of your eye, you see Riley, laying on the patio on a towel, with a lime wedge and salt in her hand.
"It's not hard Alli..." She sprinkles the salt on her belly. She has the bottle of Jose in her hand.
Before you can say anything, Alli licks the salt, and Riley dribbles the tequila over her belly to run down into her cousins mouth. Alli slurps up the dripping booze, and Riley squeals.
"Hey! What the hell!" You yell over. "No body shots! Come on girls, I take my eyes of you for one second." Alli looks thoroughly chastened, and slides back into the pool. Riley just has a look of fake innocence painted on her face.
A brisk splash of water soaks half of your shirt. "They're just having fun, James! And no one's going anywhere! Let 'em be! At least Allison isn't glued to her laptop or iPad."

You glare at Karen, but you relent. "Ok, Karen. But remember those words later."