You could always check out if there is a good Suzuki Violin/Strings teacher in your grandchild's area, though that would require some dedication on the part of a parent as well.

Starting with drums, rattles, etc. is a good idea anyway, as that will build the rhythmic base for later exploration. Also those annoying little xylophone things, or a cheap uke that she can totally trash.

If you play an instrument, play it for the child starting early. My mother and I used to make up stories on the piano, and she sang to me with her guitar when I was still in the womb. I'm very musical, or so people tell me. ;')

Just make music a normal, natural part of her life. Don't push it though. Always have it be fun in the early stages at least. If she wishes to dedicate herself to it when she's older, she can do that when she has the emotional, physical, and mental resources to do it well.

Have fun!
~*sirepseh*~