the music tree is a great book for beginners. in general, i wouldn't jump into more advanced stuff, without some focus on the basics, because a lot of piano is repetition and muscle memory as well as the theory and understanding...but if your DS grasps concepts quickly, you can simply move through the material at a faster pace, but the repetition is a necessary component in the process.

i'm personally not a fan of the suzuki method, because it puts zero emphasis on musicality, and so, kids usually end up playing the notes by rote, having little to no artistry in their actual playing. ends up sounding robotic, imo. of course, this is coming from someone with a degree in music (aka, a bit of a music snob wink ), so this may not apply to/bother you.