I'm currently running a 10.5T in my TC5x and it goes pretty good. My other touring car has a castle 5700Kv motor, and it's a fast motor specially on 2S and 3S LiPo. If your daughter will be driving it - I suggest turning down the end point a bit until she gets used to the speed. Between the 2 - the 5700Kv might be a bit much (IMO); I would go with a 10.5T or 17.5T the most.
This is what I have in it right now: http://www.speedpassion.net/us/produ...=SPF10V2&c=MTR
There's a combo set for under $100: http://www.speedpassion.net/us/produ...12280175&c=CMB
You can probably find it cheaper from a hobby shop somewhere for less. http://www.tqrcracing.com/
has them on sale right now for $89
Make sure you have extra arm mounts (and shims), c-hubs, and arms. Those are the parts I broke / lost when I first got the car.