Bowling requires the children to aim and roll a ball toward a target. Commercial bowling pin sets for kids work, but you can also make your own set using recycled materials out of 2-liter soda bottles. A small amount of sand in the bottom of each bottle gives it some weight so it doesn't tip over to easily. Set up the pins in the traditional formation (one in front, followed by rows of two, three and four "pins"). Supply a plastic play ball or soccer ball to knock over the pins. Start with the kids about five feet from the pins. Once they master the task at that distance, move them back further.
The carnival game requires the tosser to throw a ball through a small hole, but that can be quite a challenge for preschool kids. Use something with a large opening, like a laundry basket, as a target instead. Set up three baskets at different distances from the throwing line. Place the first basket one foot from the throwing line for an easy target. The second basket should be at least two feet away and third at least a foot beyond the second one.
The duck pond is another classic carnival game that works well for preschool kids. The players catch a rubber duck floating in a kiddie pool. Each duck has a number, letter or symbol drawn on the bottom that indicates a prize.
If you don't want to mess with water, create a cardboard "treasure chest" and fill it with beads. Bury several large coins made from cardboard in the treasure that indicate the prize. Provide the child with a toy shovel to dig through the treasure to locate a prize coin.
Modify the traditional cake walk game to include small toys as the prize. The set up includes squares taped to the floor in a circular pattern, with at least one square for each participant. Each square holds a different symbol or number to distinguish it from the others. As music plays, the kids move around the circle, stepping on the squares as they go. When the music stops, the kids have to stop on their current square. A number or symbol is drawn and the child standing on the corresponding square gets to pick a toy.
A short obstacle course for kids this age could include cones to weave through, mats or bean bags to crawl over, a tricycle to pedal over a short distance and a few very soft balls to dodge. Those balls would be tossed by two adult helpers. When the children hit the finish line, celebrate with a spray of silly string.
Inexpensive trinkets delight young children, particularly when they're prizes won at a carnival. Plastic animals, bouncy balls, bead necklaces, bracelets, toy cars, candy and balloons should do the trick. Check at the local dollar store or party supply store for inexpensive bulk packages.