While using your touch stick, guide your dog around in a circular motion and as he makes a full turn, click and treat.
Do this a couple of times, eventually adding a hand signal like a circular motion with your index finger.
With time, use the touch stick less and when your pet can spin without the touch stick, add your command.
Practice until you succeed, and involve your kid in the whole process. Remember, no one loves mindless spinning more than dogs and children. They will become the best of spin-buddies.