I think it was at this age I first enjoyed your own History of Western Philiosophy. But I assume you read it to him as a bed time story?
And your first volume of your autobiography, though I expect he knows your family stories.
The White Goddess, though not by you.
I also think that this was the age when I started to read historians and social theory, . In my day it was eg Christopher Hill, EP Thompson, Ladurie’s Montaillou, Asa Briggs, Willmott etc. How about Simon Schama, Sebag-Montefiore, Antony Beevor?
And now is the age to read Hardy if he hasn’t.
Tim Mackintosh -Smith’s travel stuff is delightful.
What about Utopia, Candide and Rasselas?
If he likes primary sources, Pepys 1660 and 1665 are jolly good, or an abridged Pepys and for scurrility Saint-Simon, again possibly abridged.
Prob too young for him in the first volume but if he hasn’t read it, the complete Once and Future King. The sword in the stone is young but the rest is harrowing, you will remember.