Ok, here's advice from a girl who's cut her brother's and guy friends' hair for years:
Put the shortest (or second shortest) plastic attachment on and shave the whole head that way. Or do the shortest in the back and on the sides, and the second shortest on top if you like.
It won't look completely shaven with the plastic attachment on, and 2 weeks from now it will be long enough to look cool. You might even tell people you changed your hairstyle specifically for the fashion show! Short hair is cool on guys these days, anyway. And even if your pals wear it much longer, they'll think you are one step ahead fashion-wise and admire you for it. Just wear your new style with courage, and it'll be grown out in a few weeks, anyway.
Have fun with your new style!