I’m trying to add two additional options to the form to send a message or an announcement. Namely the following options:

* Send email
* Send SMS message

For this I have done the following:

add_filter( 'fep_form_fields', function( $fields ){
  $fields['send_message_sms'] = array(
    'type'      => 'checkbox',
    'value'     => '',
    'cb_label'  => __("Send an sms", 'my_theme' ),
    'priority'  => 35,
    'where'     => array( 'newmessage', 'reply', 'shortcode-newmessage', 'new_announcement' ),
  );

  $fields['send_message_mail'] = array(
    'type'      => 'checkbox',
    'value'     => '',
    'cb_label'  => __("Send an email", 'my_theme' ),
    'priority'  => 35,
    'where'     => array( 'newmessage', 'reply', 'shortcode-newmessage', 'new_announcement' ),
  );

  return $fields;
});

In the function fep_action_message_after_send I can check if a message can be sent or not.

But I have two problems:

1. When sending a message, the 2 check boxes are shown. But when I create an announcement, they are not.
2. How can I check the value of the checkboxes before the email is sent? To prevent sending if checkbox is not checked.