Really? I'm not too knowledgable about 8-yr olds and I'm certainly not telling you what to do with yours, but if you were to get them to explain what they learned about the binary counting system you feel that it would make sense and reveal that some underlying concepts were genuinely understood?
You can see my other comment on here, but hours after the demo I asked my 8yo to explain binary to my wife. He explained how 101 in binary is 5 pretty well.
That's fair and I don't blame you for being suspicious of my testimonial. I built the widget that's used in the demo. My son didn't play with it until the entire demo lesson was complete. He liked the lesson and learned binary from it -- something we hadn't taught him elsewhere. He asked to do it again on another day. He then went on and did two of our other unreleased lessons on his own and enjoyed them. As a parent and as someone who helped build this, I was excited.