For him: To pull off Will's preppy look, you'll need a button-down, tie, and vest (paired with jeans to prove that you're still "hip" with the kids, of course). Feel free to go overboard on the hair gel, and burst into song as much as you'd like.
For her: Emma loves color, so you'll have to pick a similarly bright (but perfectly prim) ensemble. To put it all together, try a blouse, cardigan, and skirt (floral prints or accessories are especially good). A red bob should complete your transformation!
Photo courtesy of Fox