Make a backyard bowling alley. Add food coloring to clear plastic bottles of water. Use party streamers as lane margins. Add glow sticks for night bowling. (These would make great outdoor table nightlights also with the glowsticks, gonna try it!
Fun outdoor game for kids and adults. Use frisbees and paint the back side of them. How to make a unique bean bag toss game from terra cotta pot saucers and a printable (which you can get for free by clicking through!