My daughter originally had my 2nd hand iPod Mini at the age of 8...she just picked it up and used it straight away. I loaded it with all the music she liked at the time..so there was no thought of her having to use itunes...her listening pattern stays quite stable...perhaps a new album every few months when I decide to introduce her to something new

Good thing with the pod is you can set the sound limit - what ever you choose I'd recommend making sure you can do that.
Em is now 10 and has upgraded to an 8gb ipod Touch...she bought a JBL StageIII dock the other day from selling the top prize she won in a raffle lol Even though she is tech savvy and creates her own web sites and does various quite incredible stuff on her own I still sync her pod for her.