"Talented" I think mostly is used to describe people who practised something every day for many years. You will only do that if you like/love/enjoy doing it.
I started music lessons at 4 and still make music every day (age 50). Also I love chess and programming. ..How about music?
I understand that it may not be fun, but the idea is to build a good foundation,a framework upon which other things can be built upon.
So to that end I'd say chess. It would be terrible to grow up hating programming.
It sounds like the approach you will be taking will not involve fun. That's fine, but I think it needs to be acknowledged. Forcing them to study a subject will be work to them. The fun way is to let let them explore chess and programming naturally and build their knowledge out of a desire to increase their skill/pleasure in the task, but then "they may not take the best decision".
If the stuff you have planned for them may not be fun, that makes emotional development all the more important.