I need help with clothes!!!?

ok,i'm going out to this fancy place called California Dreaming and i dont know if i should wear a dress or wear a khaki color pants and a white top. I live in South Carolina so,its pretty hot but today is kind of chilly. It is 47 degrees. But dont try to get to fancy on me because i am only 10!!! But im very mature than some other weird girls. please answer my question!!!