As the Columbia Threadneedle Investments Boston Triathlon enters its 15th year, there are plenty of reasons for both spectators and participants to cheer. Taking place the weekend of August 26 & 27 and centered around South Boston’s Carson Beach, the Hub’s only triathlon features both Olympic and Sprint distance races involving running, swimming and biking, while also adding a new Team Championship competition that’s open to all comers. The main race on Sunday is preceded by a free Kids Day on August 26 that offers a fun day of activities meant to inspire future triathletes, including an opportunity to compete in a Splash & Dash run/swim race. Stick around for the post-race festivities on August 27, where onlookers can mingle with the racers. Check the website for details.