Candy Game
Have the 12-year-old kids sit around a table and give each one two plastic bowls. Fill one bowl with small candies, such as M&Ms or Skittles, and give each player a straw. Set a time for one minute. When you say, "Go," the kids must suck the candy to the bottom of the straw and transfer pieces to the empty bowl. They cannot use their hands to touch the candy at any time. After one minute, the player who has the most candies transferred to his empty bowl wins the game.
Crazy Hat Exchange
Place crazy hats in paper sacks (one per guest) and number the sacks. Write the numbers 1 through the number of guests at the party on small slips of paper and place them in a bowl. Give the birthday child the number one so she can go first. She must select a paper bag, open it and place the crazy hat on her head. Number two can either take number one's hat or open a new one. If she takes number one's hat, she can go get another one before number three selects next. This repeats until each player has a hat. Number one, the birthday girl, can swap hats with any player in the game. Crazy hats are available online and at many party supply stores.
T-Shirt Game
Divide the players into teams of four and give each team an over-sized T-shirt. Have one player put the shirt on and have another player on the same team face that player, while holding his hands. When you say, "Go," team players three and four must transfer the shirt from player one to player two. The players cannot let go of each other's hands. When player two has the shirt on, player three must hold his hands and the teammates must transfer the shirt to player three. The first team to transfer the shirt all the way to player four wins the game.
Feet Rolling
Tell the 12-year-olds to select a partner and have them take their shoes and socks off so they are barefoot. Mark a starting line and finish line about 20 feet apart. Have them lie down on their backs with their feet touching their partner's feet. When you say, "Go," they must roll to the finish line with their toes and feet touching the entire time. The first team to roll over the finish line wins the game.