When you create the checkboxes, you don't attach any events to them. Your loop to disable the input only happens when you create the checkAge part of the form, and never executes again. If you attach an even to the checkboxes, then it should solve your problem.
Also, your checkAge function adds the checkbox inputs to the document, but you never update your inputs
array to include the checkboxes.
You may want to consider adding all the HTML elements to the page initially, and using display:none/display:block to hide/show the elements.