If you want to do this writing a custom code here is one solution:
while saving the node call a submit function
$form['#submit'] = 'your function';
Check the value of the radio button and provide the $to parameter accordingly.
then use the snippet below to send the custom email through your module
$module = 'module_name';
$key = 'key for the email';
$to = 'mailaddress';// which you set above according to the selected radio value
$language = language_default();
$from = 'from_email_address';
$send = FALSE;
$subject = 'subject line';
$body = 'body of the email';
$params = array(
'subject' => $subject,
'body' => $body,
);
$message = drupal_mail($module, $key, $to, $language, $params, $from, $send);
$message['subject'] = $subject;
$message['body'] = array();
$message['body'][] = $body;
// Retrieve the responsible implementation for this message.
$system = drupal_mail_system($module, $key);
// Format the message body.
$message = $system->format($message);
// Send e-mail.
$message['result'] = $system->mail($message);
if ($message['result'] == 1) {
drupal_set_message(t('Mail has been sent to the user'), 'status');
}
else {
drupal_set_message(t('Mail was not sent'), 'error');
};