Scratch is designed to teach the basic concepts of coding, but doesn't really have practical application outside of their tutorials. It can be helpful if your child's math, keyboard and logic skills are still developing. Their interface is a little clunky, but it the underlying ideas are a bit more sophisticated.
Code.org has some Scratch-esque programs as well. However, they also will point you to Khan Academy, Codecademy, Grok and other sites to learn Javascript, Python, etc. which are standard languages. They have also partnered with licensed brands like Angry Birds to teach coding, which can be a tempting hook for some kids. Scratch has no bells and whistles like this.
So, if your DS6 has some math/logic skills around 4th grade+ and is semi-comfortable around a keyboard, you may want to skip right ahead to Khan Academy. If not, then either Scratch or Code.org would be just fine to learn basic logic and concepts while the math and keyboard skills catch up.
I would recommend trying the initial tutorials on both Scratch and Code.org yourself and you'll get a sense for how the sites try to teach. You'll know better than us which style would work best for your son.
