I figure I need to practice my legacy lens skills so I want to challenge myself by shooting action. I have a Nikon Nikkor 50mm f/1.4 lens and I'm planning to shoot my son's "bike day" at his preschool. Picture about 25 4-year-olds riding their bikes around an oblong track-like area that's about 10 meters long. Any tips for shooting this type of action? They won't be going super-fast, but they will be moving. It will be mid-morning on a bright sunny day. Should I choose a middle-of-the road aperture like f/8 or f/11? Or should I pick a shutter speed that will stop the action, like maybe 1/500 or higher? Should I just pre-focus on a certain spot and wait for the kids to ride by?