A great place to start looking for ideas would be your local entertainment rental shop. If you don't already own a bounce house (or don't want to purchase one), you can choose from a nice selection. They also offer a wide variety of carnival themed rentals. Here are a few ideas from the rental company:
Birthday cake or cupcakes decorated with colorful candy confetti and clown candles/motifs

Party Game Ideas
Balloon Pop
Purchase a large corkboard and staple small inflated balloons in rows across the board. Prior to inflating the balloons, you can slip a numbered paper inside that correlates with a small prize. Make sure you use metal tipped darts so that balloons pop.
Ring Toss
To make rings, purchase clear flexible tubing from your local home improvement store. Cut to length to fit your desired finished ring size and then fill each tube with colorful confetti (if desired) and use a connecter piece made for your sized tubing to connect the two ends, forming a ring or securely tape the ends together with a heavy duty clear tape.
Purchase smaller diameter dowel rods, paint in bright colors and cut long enough to be inserted into the ground with enough above ground to catch the rings. You can also used empty 2-liter soda bottles filled with sand but make sure to set them on a flat surface so they don't fall over.
Duck Game
Fill a small, inexpensive kids pool with several inches of water.
Purchase rubber ducks and write either names or numbers on the bottom of each with a permanent marker which corresponds with a prize.Basketball Game
If you have a basketball hoop, mark a line on the ground with tape for all players to stand behind and give a prize to the player that makes three baskets out of five etc..
Penny Toss
Buy several sheets of foam board, taping the seams together in the back and attach stickers in the same size in rows down the sheets. Lay on a flat service and let guests toss pennies onto the center of the tickets to win prizes.
Tin Can Game
Using clean, emptied soup cans of the same size, build one or several pyramids. If you prefer to add a bit of weight to them, keep the open side up and fill each with a small rock, beanbag etc., just be sure the item is easily replaced in the can after each game (loose sand etc. would not work!). Depending on the weight of the cans, use either a beanbag or tennis ball to try to knock all the cans of the pyramid over in order to win a prize.
Ball Toss
Arrange several baskets of different sizes on the ground or you can screw some into a sheet of painted plywood and lean it up against a tree so that it's slightly slanted to help catch the balls. The smaller baskets are worth more points. Award different prizes on a point system.
Goldfish Game
Use small,wide-mouthed, disposable,clear,rigid plastic cups and tape the bottoms with a strong double-sided tape. Make an even amount of rows going in all directions and fill a small sand pail with ping-pong balls. Let players toss balls until they win. Prizes can be prepackaged bags of Goldfish crackers, gummy fish etc.
Decorations