I’ll be controversial here and point out that if you’re using a pre-built theme as massively “heavy” as you are, then honestly I wouldn’t even worry about minning CSS files!
I’ll go out on a limb and guess you are also using a bunch of plugins (my bunch is 6+) in which case why not just go ahead and install a CSS minning plugin as well, and have done with it?
From an actual devs point of view then sure you can min the code in your child theme for (presumably, there’s little of it) minor benefit. Or you can min the CSS in the main theme and get (larger…I bet there’s 5k lines+) benefits from doing so – until you update the theme and it “un”mins gain.
Honestly, I would either:
- Learn to craft you own theme – lean mean, fast to load and professional
- Use the “divi” theme and forget about it
- Employ a minning plugin
…in that order 🙂
The demo here: http://www.elegantthemes.com/demo/?theme=Divi shows 12 CSS files and 24 JS files being loaded. So again, I just feel there’s a slight disconnect between using a theme like that, and being concerned about load speed. You might as well buy a Ford Fiesta and then worry about entering it into a drag race 😉