Hello! I have an almost 9yo as well. I'm not sure if you plan to homeschool full time or are only asking about learning at home during the summer. I guess you could very well let him hold the cards as it sounds as if you're doing a great job at it and he's enjoying himself.
That's a great idea about creating his own Greek God. Wish I'd thought of it!
If he is very interested, there's a National Mythology Exam that he could try. The book used to prepare for it is the D'Aulaires Greek Myths available in most libraries.
http://www.etclassics.org/nme.htmlhttp://www.amazon.com/DAulaires-Greek-Myths-Ingri-dAulaire/dp/0440406943/Reading the book should prep him enough but there's also an online course available from Athena's Advanced Academy. The benefit of using A3 would be that he could learn together in an online class environment and the instructor makes it rather fun.
http://www.athenasacademy.com/One of the things my son did with Greek Myths was to illustrate a notebook and also a family tree of the gods. My son doesn't like to write so illustrating was a fun option. The Percy Jackson series (if he hasn't read it already) may also be a nice spinoff. And we took him to places that had statues of Greek gods and he had fun identifying them.
We homeschool year round and follow a "whatever-works" strategy be it for resources or scheduling. But if you're afterschooling or doing it during the summer, I don't know, maybe you'd need a schedule if you want to accomplish something specific? Hopefully others will have better answers for you!
All the best!
