Freeze!
You'll need a whistle for this one. Set an end point on the jungle gym for the finish of the race. The highest point will typically be the best option. Start the race a little bit away from the jungle gym and line the children up. On your first whistle, they will start running toward the structure. On the next whistle, they have to freeze in place. If children move when they should be frozen, then those children each take three steps back. Each subsequent whistle will unfreeze and freeze them. First to the top wins.
Ring the Bell
For this race, you will need a stopwatch and bell. Place the bell at the highest point on the jungle gym and the children will take turns running up to the bell and ringing it. Set a predetermined amount of time on the stopwatch and see how many times each child can ring the bell and come back to the starting point within that time period. The kid with the most rings wins the game.
Jungle Gym Tag
Kids often play tag on the playground, but this is a variation of the game they're used to playing. In this game, all the children start on the jungle gym and must stay on it the whole time. If the child who is "it" sees that there is another player touching the ground, he yells, "Monkey on the rocks!" and that player then becomes "it." This makes the game of tag more interesting and slightly more difficult.
March of the Ants
Play music for the children as they march around in an area away from the jungle gym. Once the music stops, they need to scramble to the jungle gym; they're not "safe" unless their feet are off the ground. Pick one child or a parent to be "it" and chase down the ants and try to catch them before they reach the structure. The person caught becomes the next "it" and the game starts over.