Graduation party outfit? *tenpoints*?

Okay, so today I'm going to my friend's graduation party. It's not fancy or anything;it's a barbecue. So the other day was my graduation, and I wore a pretty low cut dress. That isn't too important though. So today, I was planning on wearing some new shorts, and some random shirt. The shorts are Aero, and they are pretty short. I'm not fat, but I'm not skinny if you know what I mean. SO I'm kind of scared to wear these shorts, because I don't want people thinking that I'm a slut/skank or something like that. Especially since I wore that dress before. So what should I do? There will be my guy classmates there, and my friend's older sister and her friends, and her parents. PPPPPLLLLLEEEAAASEEE help! Thanks!