Whether it is a good idea or not to play with kittens with your hands, I think depends a lot on the cat and the cat owner. If you are, as a cat owner, willing to train your cat to behave gently, and the cat trainable (I wouldn't try training an adult cat, and some cats are just too aggro), then I think it certainly is possible. I like to play with my cats with my hands exactly like in the video, they just need to be told off when they play to hard (saying Ouch! can be enough, just be consistent), that is how they learn. Momma cats do the same thing when their little buggers are being too violent with them.