Bean Bag Toss
Use foam or plywood and paint to create a cute and entertaining structure for kids with a hole cut out or another structure that is large enough to toss a bean bag through. Many times these structures take on the form of some sort of animal with their mouth open for the bean bag. You could also build a structure that has more than one hole cut through it, depending on the grade level and ages of your participants.
Bouncy House
A bouncy house always seems to be a hit at festivals and parties. These are also great for younger participants in the crowd. Check the phone book for party rentals in your area. You may consider getting more than one bouncy structure to avoid long lines and frustrated kids.
Bowling
Set up bowling pins made from soda bottles with a bit of sand in the bottom of them. Use small foam or rubber balls, or even a bean bag to try and knock the bowling pins over. This game can be adapted for older and younger children by moving the children closer or further away depending on their size.
Bobbing for Apples
This game is tried and true, but is almost always a hit at festivals and carnivals. Grab a metal bucket, some small apples, and some water to fill up the bucket. Players use their mouths to try and catch the apples in an allotted amount of time. A towel will be much appreciated when the players are done.