I firmly believe most horses will never be reliable mounts for begginner children. My Arabians are well trained, but I would never put my kids on them. They are too sensitive. Too much leg and they would be off like a shot. Falling off a bolting horse on your first couple of rides might spoil any chance of that child's continuing interest in riding horses. Not only that, but also teach some nasty
Habits to the horse. If you don't have a laid back dead broke horse, I would get lessons for the little ones. I am not saying a child cannot handle a quick Arabian. I just think confidence and experience need to be obtained first. Just my opinion of course. Good luck!