Just HTML with CSS is actually a great way to develop some basic programming skills in a child-friendly way. HTML is the language that web pages are written in and allows you to structure a page with headings, paragraphs, etc. CSS then allows you to say what those elements should look like.
These are the technologies that much of the web runs on, and increasingly the technology set that a lot of apps will be developed with. They happen to be my preferred technologies to work with so it's definitely the path we'll be taking with our kids.
There are lots of educational materials around for these technologies and there are jobs that require these skills.
Web technologies can have a bit of a getting started problem if you're completely new. Coder nicely fills that spot by pulling the tools together and providing an environment with a web server to run code on. And the fact that it runs on a Raspberry Pi is very cool. (We have a couple of Raspberry Pis.)
Here's the video that explains the idea behind Coder.
CanaKit Raspberry Pi (512 MB) Basic Kit (Raspberry Pi 512 MB + Clear Case + Micro USB Power Supply)To get started with Coder you'll need a Raspberry Pi with an SD card, power supply. Hopefully you already have a spare mouse, keyboard and display that you can use. Oh and a Wifi dongle is handy too, as is a USB hub.
Note that when they say "a little download" in the video that's not really true. It's over 1GB and will take a while to download, so make sure you're prepared for that and don't have an impatient child expecting to be up and running instantly.
Coder runs in the Chrome web browser which makes things very straightforward. You develop and test in the same place. (I'm a fan of the Cloud9 web IDE which takes the same approach for professional development.)
You might wonder why Google have targeted the Raspberry Pi rather than providing a cloud-based service. Personally I think this is a good move. Whenever you have an online service for kids you hit all the regulations like COPPA. Of course the regs are there to protect kids but they can be a real pain when you want to get access to dev tools for them.
Scratch seem to manage to provide an online community for coder kids, but Google tend to put age restrictions on their services. For example children need be be at least 13 to use Google Documents and Drive. Well I really don't want to have to wait until my sons are 13 to teach them Word processing! I use Google docs and have no interest in teaching them MS products or other less mainstream tools. (Yes, I'm aware there's a schools program, but not at my kids' school.)
I'm very glad that Google have made Coder available in this way so it can be used at home behind a firewall without hitting those issues. It also make it easier for schools to make use of the tools without having to sign kids up for online accounts.
Definitely a good addition to the children's coding toolkit.
Download: Google Coder