Wren,
DD9 is one with high energy and enjoys lots of scheduled activities. I often have to hold her back, since I can't get her to several places at once. She plays the flute and have since age 7, since she didn't want to play piano as suggested by the music school. I find playing an instrument to be a good challenge for her and she likes the math aspect of music theory. Since school has been easy, this provides a good challenge and lesson on practice, hard work and rewards.
DD also figure skates, which is a great physical challenge. We have found choosing two activities (physical and musical) to be a great compliment and scheduling wise manageable.
Since I started piano at 4, and all my brothers played various instruments at various "talent" levels, I know the progress may be very slow at an early age. I did Suzuki piano which is very family involved whereas my brother zoomed through levels of violin and Suzuki was not the method for him. In the end, I play for my own enjoyment (and family's horror, LOL) and my brother travels the world conducting many great symphony orchestras for living. So the method chosen was not the determinant for success, rather than initial talent and work ethic.
