Well done, and I think you have have him and keep at it.
I too remember being in kindergarten when my father showed me how B&W photos were made. The image appearing in the developer was like magic.
I have had my son in with me on and off since he was 3. When really young James job was to lift the lid on the flat bed processor for me to drop in the exposed sheets. Then at 4 he came an helped with the Jobo - though his help was not appreciated while processing 7 rolls of E6, he decided it would be better if the colour dev and Blix were added together after the first dev wash. Kissed those films good by. He is happy to shake the prints in the bath as they develop, and show his 4 year old sister how it is to be done
Now James (seven next month) with his own P&S 35mm camera wants to process and print his pictures as soon the film is done. Something we have not managed in the same day yet.