How can I create Apple ID for a child without a Credit Card?
Sign out.
Search for any free app.
Select "Get" and "Install App".
You should see screen, that you need to log in to download. Select "Create New Apple ID".
You should see "None" option when selecting payment method.
Activate Apple ID and you have created new Apple ID for your son.


Then just sign out from son's Apple ID and log in to yours.