Here are a few activities to keep the group entertained when the novelty of spooking one another starts to wear off.
Have the children stand in a circle. Give each child a small ball of yarn. Have each child tie the wool around his or her waist. When everyone is ready, yell, "Toss!" Each child should then toss his or her ball of yarn to someone on the other side of the room. Repeat a dozen times or more until the group has created an intricate "spiderweb" and then watch the fun begin as they try to figure out how to get themselves untangled again.
Bobbing for apples
This Halloween party game is as old as the stars, but it's still a perennial favorite with kids of all ages. Simply float a bunch of apples in a washtub full of water. Give each child a chance to try to remove an apple from the washtub without using his or her hands. (Hint: The game is even more challenging if you remove the stems from the apples!)
This is a fun variation on bobbing for apples -- and one that requires every bit as much skill. Peel some bananas and hang them on strings from the ceiling (one banana per string). Note: The strings need to be long enough that the top of each banana is roughly at each child's chin level. Each child is then told to try to eat the banana without using his or her hands. (Hint: If you want to make the game even tougher, dip each banana in chocolate sauce and/or turn out the lights!)
Halloween beanbag toss
Paint a jack-o'-lantern face on a cardboard box and cut a large hole where the nose should be. The guests can then try tossing beanbags through the hole.
Halloween word game
Play this game when you want the kids to start winding down. Ask each child to make as many different words as he or she can by using the letters in Halloween, Trick or Treat, Haunted House or some other Halloween word.