My son was exactly the same. He wanted to play every sport growing up, but especially soccer and basketball. He gave up soccer a few years ago but just gave up basketball this year (he is in high school). He still plays baketball just for fun every day during breaks, or in our backyard, or with his tennis friends at tournaments. Our challenge was finding time for everything as he became more and more competitive in tennis. But his tennis coaches all agree that soccer and basketball were the best things we could have ever done for his tennis, especially for his footwork and his conditioning. Let your son enjoy it and focus instead on how it will help his tennis game -- and he will be far less likely to burn out!