Outdoor tic tac toe using stone tiles and rocks. I would make a small garden for the kids and have this in it. Cute decor when the kids aren't playing with it. Great for when the mom is at work and the kids want to play
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!