They're years away from job searching, so it's not worth worrying about micro trends (although the macro trend to AI is probably something to watch). Plus if they plan to study CS/IT at college, that should mean they don't have to learn everything on their own :)
For now though... They should probably just be tinkering with whatever they enjoy. Fostering a love of coding, sense of curiosity and confidence they can learn whatever they want is probably going to have more impact in the long term. eg. if they understand the fundamental patterns of coding are separate from any specific language or project, they'll know their core knowledge is there to help them pick up new things when they need to.
If and when they do study CS/IT at college, that's probably the time to start considering complementary skills like testing/QA, deployment, time management, stakeholder management, communication and presentation skills. But they don't strike me as fun weekend projects for a 10 and 14yo :) Hence saying it's probably better to just keep it fun.