If you take your kids through a terrifying haunted house at 3, they might never go back. For the little ones (preschoolers particularly), Halloween is more about dressing up. The chance to play fantasy and get candy are the main attractions of this October festival. If you've opted out of the haunted house, but still want some Halloween themed party, you'll need to consider three things.
Let the theme be Halloween and don't take it any further than that. I know it's tempting to add another theme. Many people do, making it a monster party or a princess party, but I'd advise against that. Halloween is the child's chance to choose their costume. If you require that she come as a princess she likely won't get the chance to be that ladybug she's been planning all year.
Decorate with orange and black streamers and balloons. String cobwebs at the door and place little plastic spiders in them. Have carved (but not lit) or painted pumpkins around the house.
Keep it to things that the children will actually eat, but make it fun. Try putting jelly worms in the pudding, or making green (snot!) yogurt. Check out some of these recipes for food that will be disgusting you when you see it and be delicious when you taste it. They include 'boogers on a stick' and 'day old bath water'. This is one chance for the children where booger humor is okay and even the adults are having fun with gross stuff. Let your little one think up some creative foods to serve their friends.
Do one craft with the children, but keep it simple so that everyone gets a chance to finish. You might want to have everything cut out already so the children can choose their pieces, but don't have to fuss around with scissors. Try making a trick-or-treat bag out of a milk carton. Cut the top off your milk jug, and decorate it. Attach a handle and you're done. This craft is for ages 3 and up. Here are the full instructions.
Other activities could include, pin the nose on the pumpkin or a Halloween bone hunt. This ghost catcher circle game sounds like lots of fun. All you need is a pumpkin and some stickers. Remember when planning your games that children in costumes might be a bit limited as far as what activities they can do.