Mine does not run "very hot" when just idling. In fact, it does not run very hot at anytime and there would be not problem letting a kid hold it. If your experience is as you say, then yours is defective and you should have it replaced.
Can you try and experiment for me if you have the time please? Run it with 100% backlight for 15 mins and see how it heats up. I'll further test myself with some intensive processing thrown into the mix but I'm pretty sure the large heat build up is purely down to the battery discharging rapidly with a bright screen.