Changing text format for a textarea in a custom content type in a custom module

I'm trying to use the CKEditor module on a textarea in a form, but the CKEditor is not being displayed. The field name is 'pages' and the following code is from the installation file. I've pasted in a shortened version of the installation file below, with only the pages field.

I've also tried using hook_form_alter to change the text format, but haven't had any luck with that either.
What's the best way to get the CKEditor to appear in the text area?

Thank you for any help!

function portfolio_edit_install() {
  $t = get_t();
  $portfolio_edit = array(
    'type' => 'portfolio',
    'name' => $t('Portfolio'),
	'has_title' => TRUE,
    'base' => 'node_content',
    'description' => $t('Content type to handle portfolios.'),
    'promote' => 0,
    'status' => 1,
    'comment' => 0,
  );
  $content_type = node_type_set_defaults($portfolio_edit);
  node_type_save($content_type);

  variable_set('node_options_portfolio_edit', array('status'));
  foreach (_portfolio_edit_installed_fields() as $field) {
    field_create_field($field);
  }
  
  foreach (_portfolio_edit_installed_instances() as $instance) {
    $instance['entity_type'] = 'node';
    $instance['bundle'] = 'portfolio';
    field_create_instance($instance);
  }

}


function _portfolio_edit_installed_instances() {
  $t = get_t();
  $instances = array(
    'pages' => array(
      'field_name'  => 'pages',
      'label'       => $t('Pages'),
      'cardinality' => 1,
      'widget'      => array(
        'type'       => 'text_textarea',
        'settings'   => array('rows' => 5),
      ),
    ),
  );
  return $instances;
}

function _portfolio_edit_installed_fields() {
  $t = get_t();
  $fields = array(
	'pages' => array(
      'field_name'   => 'pages',
      'label'        => $t('Pages'),
      'cardinality'  => FIELD_CARDINALITY_UNLIMITED,
      'type'         => 'text_area',
      'settings'     => array(
        'max_length'  => 1000,
      ),
    ),	
  );
  return $fields;
}