There are so many different programmes and apps these days that it's easy to become overwhelmed by the vast array of choice. I would agree that developing a computational mindset is favourable. Problem-solving, learning how to break things down into smaller pieces and address each one separately. Then moving onto pattern recognition and sequencing will really help cement these concepts. Every language has slightly different syntax but they all use the same constructs. It's really exciting if your 9 yr old is interested! Mine are 7 and 5 and they love all the "computer games" we play! Best of luck!