Richard Petty, more than 40 members of his family and select Xfinity Rewards members will serve as the Grand Marshals for this Sunday’s Xfinity 500 at Martinsville Speedway. Together, they will deliver the most famous words in motorsports ahead of the green flag. Petty, the NASCAR Hall of Famer, learned of the honor courtesy of his family, who surprised him with a special video. CLICK HERE to go to PrizePicks and use code ON3 to receive a guaranteed $50 once you play $5 in lineups! “So much fun surprising my Dad!” Kyle Petty wrote on X. “It’s going to be so special to have our entire family to…