Get some fresh air and exercise by making a 5-K loop around the park with your brood. Participants will start at the bandshell and wend counter-clockwise down to the lake, around the zoo and finish near Center Drive. The event raises money for the park, so think about creating a fund-raising page when you register online, and then ask family and friends to help you reach your goal. Enter at 15th St and Prospect Park West; registration for the run begins at 8am, race begins at 8:45am; registration for the walk begins at 9am, walk begins at 10am. Or register in advance at prospectpark.org/walkathon. All ages.