Creating muliple nodes from one page
There are a couple of modules to create entities (nodes etc) inline i.e in the parent form, when it's being created itself. 

When you save the form, it creates the entity AND the entities that are referencing it, but it's up to you to create the entity structure and references to achieve what you want.

I can vouch for References Dialog

However, I think you are making it too complex and you only really want one node type (kids) with an unlimited field (height), if that is your real scenario.

For example you easily create a custom form with three (or loop for x) fields and when it saves it adds the result to existing nodes, eg :

// Get and render the form somewhere.
$form = drupal_get_form('kids_height_form');
print render($form);

/**
 * Form constructor.
 */
function kids_height_form() {
  $kids = array(2210, 2043, 2038);
  $entities = entity_load('node', $kids);
  // dpm($entities);
  foreach ($entities as $kid) {
    $id = $kid-&gt;nid;
    $form["height_$id"] = array(
      '#title' =&gt; 'Height this week for $id',
      '#type'  =&gt; 'textfield',
    );
  }
  $form['submit'] = array(
    '#type'  =&gt; 'submit',
    '#value' =&gt; 'Submit',
  );
  return $form;
}

/**
 * Form submit handler for kids_height_form().
 */
function kids_height_form_submit($form, &amp;$form_state) {
  $kids = array(1, 2, 3);
  $entities = entity_load('node', $kids);
  foreach ($entities as $kid) {
    $id     = $kid-&gt;entity_id;
    $height = $form_state['values']["height_$id"];
    $count  = count($kid-&gt;field_height[LANGUAGE_NONE]);
    $kid-&gt;field_height[LANGUAGE_NONE][$count + 1] = array('value' =&gt; $height);
    entity_save('node', $kid);
  }
}


The top bit prints the form, the form constructor simply create as many text fields as there are node ids in the array and the submit handler does the same loop except also adds the result to a new delta for the height field and saves the entity.

You can also achieve this with EntityMetaWrappers and may be a bit neater but the process is very similar. (this is untested by the way and will need work to suit your needs);