Depends on a kid. Depends on his interests.
If you're just after programming a PC:
Scratch is quite popular. There's also similar thing called Blocky.
If the kid won't get into things unless that's a game:
Baba is you is a great game for kids.
He probably already has some favorite games, and many games today use LUA. So he could also start modifying a game he knows using LUA scripts.
If he prefers to drive something mechanic, like a robot:
There are some DJI products for kids, like Robomaster or Tello. Not the cheapest, but high quality. You can program these.
There are actually many programmable robots and robotic arms for kids, just search the net.
Arduino is also easily programmable, and there are many sensors, LEDs, displays, motors etc. which you can drive with it.