On Aug. 6 and 7, Carol Sly, of Falls Church, and Ronni Cinella, of Glen Allen, will ride in the 32nd annual Pan-Massachusetts Challenge, the nation’s pioneer charity bike-a-thon that raises more money than any other athletic fundraising event in the country. They will be among 5,000 cyclists who will ride with the collective goal of raising $34 million to support lifesaving adult and pediatric cancer care and treatment at Dana-Farber Cancer Institute through its Jimmy Fund.