When Peyton Dennis told his mom, Katie Ann, that he wanted to run in the kids’ race at the Pottersville Sod Slingers lawn mower race weekend in Pottersville, Michigan, on August 24, she wasn’t too surprised. “Peyton’s always been an active kid. He wants to do what all the other kids are doing,” Katie Ann, who lives with her family in Ionia, Michigan, told Runner’s World. “When he found out there was a race that weekend, he insisted on doing it—even though he has trouble walking now, let alone running.” At the end of February, 5-year-old Peyton was diagnosed with...