is installing a module on a live site ill advised? I am trying to install Code Per Node on my website. 

All i have to do is ad content types that would accept HTML5 webgames.

There would be theming involved.

Is this a no go?
I successfully installed modules on sites with thousands hits a day. Maybe even an hour. And I must tell it's not wise, from the point of my experience. Sometimes you have no choice (installing captcha on the spam wave when client forbids technical break), but way to many things can go wrong. If your site has any significant number of visitors and you care about your reputation, either:


Install module on a copy of your site
Put your site in maintenance mode
Add .htaccess "maintenance mode" screen
Sync files
Sync data


Or simplier, but with longer break:


Put your site in maintenance mode
Add .htaccess "maintenance mode" screen
Install module


That way if your site dies, visitors will see nice static html screen saying "Sorry, technical break" and you will be able to revert from backups.