Well done
@RF for doing some coaching, I fear on this subject you may get conflicting advise on this forum as people have very different views on coaching and how much youngsters need.
For me you're first instinct is always the right one, 100 per cent let him bowl naturally, if its a leg break action coming out as a googly that's a fair skill in itself for someone 11 years ago. I would be looking at his basics and making sure delivery is in the right place and also trying to encourage his batting if the kid wanted to improve it as well.
talking and explaining leg breaks may spark an interest as he develops if he wants to.
as I said, you may well receive conflicting advise, I have done an ECB coaching course but learnt the game thru older players at my club, and my own belief is coach the basics but let natural young players develop without altering what comes naturally to them
well done for getting involved.