Cats love to climb and explore their surroundings, so a great way to change up playtime is to have your children create an obstacle course for your cat. Look around the house for objects your cats could climb on or walk through, like laundry baskets, hula hoops, boxes and stacks of books. Once your child has set the course up, have her walk the cat through the obstacles, using a favorite toy or (for advanced cat trainers) a clicker to entice the cat into follow along.
After kitty has run the gambit a few times with encouragement, see if he will attempt it on his own. Give your child a stopwatch and make a game out of keeping time. After your cat has mastered the course (or grown bored with it), your child can switch it up by moving the objects around to create an entirely new challenge.