Here is how to change the parent slug permalink and also apply it to the children.
For example if you have:
http://example.com/monthly-event-list/child-page/
And you want to change it to:
http://example.com/events/child-page/
You would do the following in htaccess:
RewriteRule ^/?monthly-event-list/(.*)$ http://mysite.com/events/$1 [R,L]
And to add it into htaccess include it like this:
RewriteEngine On
RewriteBase /
RewriteRule ^/?monthly-event-list/(.*)$ http://mysite.com/events/$1 [R,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME}/index.html !-f
RewriteCond %{REQUEST_FILENAME}/index.php !-f
RewriteRule . index.php [L]
The above code can be credited to: http://legacy-documentation.concrete5.org/tutorials/changing-parent-page-and-keeping-old-child-urls-active
To add this in WordPress to the redirection plugin it would look like:
Source URL: /?monthly-event-list/(.*)$
Target URL: /events/$1
* Be sure to enable regex. Save your redirect then go back to edit it and you will see a regex box on the left that must be checked.