Best sport for children I think should be any martial arts related like karate. Give the children some great self-confident and positive attitude.
Give the kid something, say a ball, he or she will throw it away. Bring it to the kid again. He or she will throw again, and you will have to go and get it. Once you do, he or she will start enjoying it and laugh. Keep on doing this till you are tired or till the child grows tired, whatever occurs first. In this way your kid can pretty much turn you into a dog.
Any sport is good for kids as long as they enjoy it. Its amasing how young kids can do things, my kids where surfing at 4 and body bording way before that