What is the 'Drupal way' to create a menu callback and display a rendered page of JSON? I have created a new menu item and a callback function.

  ...
  $items['user/%user/enquiries'] = array(
    'title' =&gt; t('Enquiries'),
    'page callback' =&gt; '_client_enquiries',
    'access callback' =&gt; 'user_access',
    'access arguments' =&gt; array('view enquiries'),
    'type' =&gt; MENU_LOCAL_TASK,
    'weight' =&gt; 1
  );
 ...
 function _client_enquiries() {
   return t('Enquiries');
 }


I am now going to CURL some json from a published google spreadsheet, and cherrypick, and then print some of it out in a table. My question.. what is the drupal way to do this? I think it would be to create a custom theme function which makes my processed json data available to a template, which I can somehow load onto my menu callback and output. If that is the case, could anyone give me some pointers/examples or a point in the right direction.
Much simpler:

function _client_enquiries() {

  $var_to_output = caculate_value_to_return();

  drupal_json_output($var_to_output);
  drupal_exit();
}