Ask HN: Good first hacking computer for a 7yo

I'd like to get a computer for my 7yo son - something they can hack at, explore, learn to code, paint silly things. Might as well make it not Windows. What suggestions do people have?

The RPi integrated into a keyboard looks very cute. What is it like performance wise? Not that I need a lot, but would be good for a vanilla Linux distro to run effortlessly and lag free.

Equally, the form factor of a laptop is tempting. He can play with it at his desk, then come around and show me the result.

Any practical experiences and product recommendations very welcome!