The pain train
I was in the same boat as you for a while; I had ample experience over a few years where I worked on open source projects and websites for small-scale clients.
The easiest way to actually have freelancing on your CV? Put it there as previous work, and have some of your clients be references. It's as simple as that. As for the question of "will employers see it as valuable?", well, just put it there. Give them examples they can look at.
You're a web developer, which makes it really really easy to show off your frontend skills. We're also at the point where pretty much any developer these days has a Bitbucket or Github account, so there's the backend stuff.
Stick the websites you've worked on in a portfolio, and specifically target potential clients or employers with this (you can probably cram the usual HR buzz words in there somewhere, too).
Be sure to link said portfolio gratuitously in your CV and covering letters, too (I put mine at the start and end of my CV, make it short and sweet, and let the client take a look for themselves if they're interested.)
This one is web development-specific, too.
If you intend to be working with a business on any kind of backend code as a programmer (not a designer), you should learn the methodology and way of thinking behind nearly every framework for web development: MVC. It's also known as separation of concerns, too.
If you understand MVC, you can grasp nearly any framework in about a day or two of playing around with it.
Long story short: just put it down as normal experience, and if you enjoy the work you do, do more of it (the only way to get better at programming is to do more programming, for example). Start small if you like, and build up notability and a strong reason to get a client or a job.