Of course this would be a useful question if you were doing a qualitative research study involving interviewing X subjects. Questioning information sources also involves knowing where to look and how to look. They want AN answer to precisely the the question they've asked. Questions need to be seen as infinitely flexible and malleable. It's a lot easier if you look for information related to these shape-changing questions rather than for AN answer to A question.
Age is no barrier to modelling, demonstrating, discussing, checking questions.
You can read simple information and ask children to put their hands up when they think that it says something about what they need to know. Having a 'need to know' mindset is a lot healthier as a base for developing effective questioning than being wedded to the notion of finding a pre-processed shrinkwrapped answer to a question.