Had a chat with my sons dad, who is very relaxed about the whole Eton thing having been there himself. He said, 'If to get into Eton (or any other top school) means swatting all the hours at the age of 10 then I'd rather he went to the local comp.'
That said, of course, one wants one's child to fulfil their whole potential as much as one can. Will be buying all the above mentioned books and attempting to coax him back into trying them.
Sounds like your son has a very sensible dad. Please think very carefully about what kind of person you want your son to grow up to be. There are plenty of Eton alumni around in public life for you to look at and decide if you aspire to on your son's behalf. 'Potential' is a big word - we all have the potential to make a difference and become exceptional human beings, but it doesn't mean we have all been to Eton. Memorable and special people aren't always the ones with the flash educational credentials.