Coaster brakes are terrible for beginner cyclists, because you want your feet down as you come to a stop, but you have to keep a foot on the pedal to stop. On the other hand, hand brakes are often too hard for small hands. I tell beginners before they start, that when they want to stop they must first decide which foot to put down, then make sure they use the other foot to apply the brake. After a while they dont have to think about it; Its just like getting used to clipless pedals.