I've been playing with quads for quite a while. While you can get cheap ones from about 3 to 5k, quite some practice because you have to constantly adjust the pitch, roll, rotor speed just to hover and the little ones get frustrated and give up quite fast. I've had to settle on the models with internal gyros and proximity sensors. I recommend forking out around 10k and going for a Parrot Mars Airborne Cargo Minidrone. Works better for kids when you release the controls it automatically hovers (even in slight winds), then you simply tilt the phone to control it. Good for beginners, and you can always put off the main computer for "manual" mode