Or the cheap ol' alternative when I was a kid: wood blocks on the pedals. She'll grow quickly. :-)
We got our C'dale tandem when my daughter was 8. I had to take the reflector off the stoker seat post for it to drop low enough. If it hadn't, next on the list was replace the suspension seat post with a standard. She's now 20 and has been my main stoker all these years. Her goal for this year is 2k miles, complicated by the fact that she's in college in another state. I guess our summer is planned already... :-)
When we first got the tandem, it took a while to track down a random creaking noise. Finally, one day when it was occurring, my rear view mirror caught the top of a helmet bouncing in and out of view. She was bouncing on the suspension seat post.