For changing friendly URL’s from clubs to committees, is it just a case of updating the friendly URL and that is it, the real URL just stays the same? Or would I change both?

Are there any issues with this IE breaks in the site.

The plan is to change the word club in the URL to committees across the site.

I am not worried about SEO as its a fully private site.

You would just change that friendly URL, the real URL corresponds with code so cannot be altered. It's worth mentioning that the root Friendly URL cannot be change (i.e. forums in /forums/topic/1-test/)