@Grinchinlaws - I always volunteered to read and trips and cooking etc etc so it’s obvious to me (although I would never discuss it with other parents). In addition, our school does groups and harder work for those exceeding and my DC always knew who got harder work. Moreover, my youngest at least, always was close to the brightest kids on the playground as well, including the opposite sex and from older year groups.
From what you describe your DS has innate natural ability and just keep encouraging and reading loads to him. He will mature. What you need to make sure is the vocabulary & comprehension building if he doesn’t sit down enough to read himself in due course - audio books and reading to him and asking inference type questions regularly. Music is brilliant for the mind too, including maths and language development, according to some research, at least.
The issue we seem to have as a society now is that screens take over far too early so those who may have become avid readers later on as teens, are increasingly less likely to do so now. However, literacy is really fundamental and that is why we keep being told to read read as much as possible with our children.
If you need to move anyway there probably is not much difference in choosing a great comprehensive with good setting. That is exactly why a lot of people do move for secondary. We didn’t want to move as we love our house so grammars were a good option for us. Besides, I didn’t want to have to pay a huge amount of stamp duty either.
I do think we need to be guided by the children. My youngest just wanted to read and do music for years rather than sports. However, he is now becoming more sporty which is great. He never was a run around boy when little. The social and emotional development of children is just as important as their cognitive development so we have to support what they choose. What they innately like doing helps them build a rapport with other children choosing similar and that helps their emotional & social development.
Regarding tutoring, although I never did it myself, my friends who have chosen great tutors with actual primary school experience have reported that their children enjoyed the actual journey and got a lot out of it, regardless of 11 plus or not. We have to remember that in a class of 30 plus they don’t get much individual attention. I have always paid for 1:1 music lessons and I am not sure it is that different conceptually.