The site provides many free flash games desinged for young kids in Korea.
Especially I recommend role play game. For example, as for the role play game of rasing pets, first, you choose your pet and then feed him. Also, you will create orders to train your dogs. The activity involves all possible use of Korean language.
While playing the game, Korean language leaners can experience the authentic korean language.
It is very colorful and fun, so it will motivate students.