Jawsmom gave you some good pointers. Especially about bringing enough healthy snacks for everyone. Chances are there will be at least one other girl in the group who's going through the same thing as you! Having a good breakfast so that you aren't hungry midmorning is important. I find that if breakfast includes some protein, I can go longer without getting hungry. Another thing to do is think of a cute summer outfit you'd love to wear, and that will help you keep focused. If all else fails, just eat 1 cookie instead of 3, as you mentioned. Learning portion control is a valuable lesson in itself.
Let us know how it goes, ok?
85 pounds lost with Vertical Sleeve Gastrectomy
110 pounds lost from highest weight