There is more to Sports and Music than meets the ear.
Sports and Music: These activities are interesting because they exercise both implicit and explicit memory.
The implicit memory involves the learning of motor patterns for the musical instrument and/or the sport; and the explicit memory involves such things as learning the notes of music and the rules of the game.
In terms of music, I have always been partial to starting children with piano. I would begin exposure around 2 years of age and move toward lessons/fun experiences as soon as the child can handle them. There are those who would warn of burnout, but I believe the opportunity to develop neural infra-structure during this window of neural hyper-growth is well worth the risk !
In the area of motor activities, I have always been impressed with ballet (for both boys and girls. It is the ultimate sport).