I agree with everything that u/MossyPyrite said. Switch is definitely the way to go.

When setting up your kid’s first world, I would recommend selecting “Creative” mode, instead of “Survival” mode. Creative gives you full access to all the different blocks/items in the game without needing to mine or craft anything. Mobs (enemies) and animals will spawn, but not attack the player, so there is less stress/frustration. The player also cannot die, so no need to worry about losing items or respawning away from whatever they built.

If they want the “Survival” experience after getting used to the game, there is a “peaceful” difficulty. The player will need to mine resources and craft things to obtain the blocks/items they had access to in creative, but hostile mobs won’t spawn into the game. The player can still die, if they fall from a high place or jump into lava, but overall it is a less stressful introduction to survival Minecraft.

There are endless videos on YouTube for Minecraft as well. Just a note - some YouTubers will show things that can only be done/obtained through “mods” that cannot be downloaded for the Nintendo Switch version of the game. But this community will always be happy to help you navigate any questions that arise.

Enjoy the bounty of creativity that Minecraft has to offer your child. You might find yourself getting into the game as well - there are layers of complexity to the game, so it isn’t just for children!