The best way for your child to learn to play their instrument...
...is to actually play their instrument!
Practicing, where you set out to improve your playing in specific ways, can come later. Many of us need to start with simply playing.
If only there were some kind of sorting hat you could put on your head to discover what instrument you were meant to play. Who wants to invest years into learning an instrument, only to learn you've picked the wrong one?
Then again, that's only a problem if you believe that there's a such thing as the wrong instrument...and if you believe it has to take years to learn an instrument!