MICHAEL J. Fox has found a novel way to beat his children's fear of the effects of Parkinson's disease - he turns it into a game. The Back To The Future actor, 46, was diagnosed with the degenerative disorder in 1991, but he uses the physical shakes he suffers as a form of play with his children Samuel, 18. twins Aquinnah and Schuyler, both 12, and six-year-old Esme. He says, "They love it. Instead of being scared, they shout, 'Go, shaky dad' and sit on my lap."