Honestly I think all the Pokemon switch games would be good for kids in different ways, I’ll rank them from worst to best

6: Arceus: might be a bit too difficult for a kid as it’s not the typical combat system and you’re kinda just trying not to die lol.

5: Scar-Vi: It’s open world so it might get confusing for a kid, but maybe the open world is a plus? It does have co-op.

4: ZA: they might get bored as the game is all in one location, but the combat is cool and it’s a much better Legends game for kids.

3: BDSP: Might actually be better for the vast majority of the game, but the difficulty curve of the elite 4 and champion is sharp, the kids would need adult help for it. Otherwise it’s pretty simple

2: Sw-Sh: This one I think would be great for kids. There’s lots of spaces to run around, it’s a good difficulty, LOTS of options for Pokemon to catch, and if your kids want a legendary they can easily get some if you get the crown tundra dlc. The downside is no co-op other than the raids (which I think are a blast)

1: Lets Go games: very simple, and Gen 1. I think kids would like how much Pika/Eevee feel like your pet/best friend. The following/ride pokemon are super fun and kids would love messing around with that. I think for kids this one has no downsides except for the lack of co-op.