Keep kids active this summer by playing fun backyard games like balloon volleyball or a create-your-own obstacle course, according to Sign Up Genius. To set up the balloon volleyball, hang a jump rope across an area and use inflated balloons to make it easy for all age groups to join in. When creating an obstacle course, get creative with cardboard boxes, ropes, hula hoops, lawn furniture, slides, and sprinklers and give everyone an opportunity to add something to the mix.