You pause for a moment, then head for the clothes for 7 to 10-year-olds. You don't want to be too young, since you won't be able to do as much as you want to do on the playground. However, if you look like an older kid, you'll look a bit lame trying to play like a kid. An 8 or 9-year-old like you were last night might be best. You grab some kids clothes, and after a moment of thought, you pick up a small children's backpack too. You need someplace to put your adult clothes and belongings.
You then turn to Jinn, who is watching you with obvious amusement. He comes closer and hugs you about the waist, which makes you stiffen a bit in surprise.
"All set, sweetie?" Jinn says in a low voice. He's really getting into this boyfriend thing.
"What about you?" you quickly ask, trying to keep yourself from blushing.
"I can role-play however you wish," Jinn replies mischievously, and you willfully ignore any subtext as you remember Jinn can change form at will, including clothes.
"Now I just need someplace to change," you mutter as you leave the store after buying the clothes, shoes, and backpack.
"The park appears to have a restroom," Jinn points helpfully. As you approach, you turn to Jinn.
"Since I don't really want to look like your kid," you ponder a bit. "Why don't you change into a middle-school kid? You can be my big brother for a little while, that way people won't get suspicious of a little kid being alone."
"Anything for you, little sister," Jinn grins at you, and the two of you enter the men's and women's restrooms correspondingly.
Thankfully, no one else is in the bathroom, so you quickly lock yourself in a stall and strip. Double-checking that no one has entered, you shove your adult clothes and purse into the small backpack, then shrink yourself down to an 8-year-old child. For a moment, you wish you could just grow your fur, tail, and ears, and run around like that, but you know better than to do any of that in public. You pull on the new clothes you just bought and grab your backpack. Exiting the bathroom on your smaller legs, you spot a very cool-looking 13-year-old boy lounging around. As you get closer, he gives you a familiar grin.
"Shall we play together for a while, little sister?" Jinn grins as he reaches for your hand.