You can turn transmitter down and gradually turn it up, but watch he does'nt crank it up to full when your not looking. Having said that with the stock servo it does'nt handle great on brushless power.
You could buy brushed as HB said then when your lad gets bored with it convert to brushless with lipos, this will split the cost and is what I did.
Unlike some others I like my carnage, it does have it's failings but fun to upgrade and easy to work on.