My DS was 8 and he LOVED this game. He found some other older boys who had notebooks full of cards who were giving him some they had duplicates of or were trading him.
Basically, you go to the place in town square and you sign up through your magic bands. You then get a packet of cards. There are about 5-6 cards in your deck and if everyone signs up, then one person can play and have many more cards. They are random packs. You are given a map and the areas of the park where these portals or magic windows are located. They tell you where you are headed from there. It is either Main St, Fantasyland, Adventureland or Frontierland.
You find a portal by also seeing a plaque on the ground. You scan your MB by a keyhole you see and then stand the plaque and you will see a video. You are fighting villians and casting spells by holding up various cards to cause certain damage. Everyone has a different random game and once you finish your first one in that land, it sends you somewhere else, so you can play as much as you want.
My 8 year old would have played it all day if we would have let him.