N.R.
J.,
My sister has 4 kids and several cats. What she did was explain to the children that the cats are like babies and you have to be very gentle with babies. Everytime they went to touch the cat(s) she would say "remember, he's just a baby and you need to be gentle with babies". Make sure you praise your son when he does treat the cat well and gently correct him when he's being too rough, you can't just yell at him. He's old enough to understand this concept and I'm sure that he loves the cat and wants to touch and hold it. This should work. Good luck!