Unlocking new characters in World

Hello all. I am missing 5 characters total and I feel like Ive been playing this game a lot. I REALLY want Conkdor and Spike as Ive been looking forward to playing as them since I got the game.

Would it be a viable strategy to play 2 players only and just have the person behind repeatedly go through the item box and try to get Kamek or did they make it so you cant do that somehow?

The unlock method in this game is the one thing I really dont like, the rest of the game is awesome and Ive been playing MK since Super Mario Kart came out when I was 8 years old.