You sound like a good dad. Your son seems to have the nack:
Ok, maybe it is a good time to learn soldering then and implement some circuits on a matrix board. Before doing so you can try the circuit on a breadboard. In this way he will be introduced to 'prototyping'.
There are abundant sources where you can find little circuits. Magazines might be a bit too complex, online you will find all levels and you can choose what is suitable. Websites such as this one have a projects section. You might also find books with beginners project in your bookshop.
Be selective about the projects you do, ask you son too. They need to be well documented and do something at the end of the day. LEDs and speakers are popular.
Also, try to blend in some simple 'applied theory' circuits like a capacitor being charged with a resistor, or a diode and an LED. Your son will develop and intuition about what components do which I cannot stress enough how important it is.
Finally, take all measures possible to shield your son from mains voltage but I am sure you have done this already. Also use an isolation transformer and a residual current breaker if you haven't. Part of the protection is to explain why it is dangerous.
In a couple years time you can talk about logic gates and other integrated circuits. Stay away from programmable devices such as microcontrollers at the moment as they are a 'black box' to the beginner.
Dont worry too much about the course of learning you take. Although your son seems to be already autonomous with his hobby, some supervision is advisable. Soon your role will change from demonstrator to student therefore be prepared to recognise your son's achievements, as I am sure you would do anyway. Keep reminding him of safety though. Since you will be the one funding his hobby for the years to come, bite the bullet and choose high quality equipment with safety certificates. Even a simple screw driver can slip and injure your hand if the tip is made from a cheap soft alloy.
If you have any questions please do ask here. Good luck and well done for your efforts.