Recommendation: Good for playing with a child?

If you search for 'baby games' on the Play Store right now, you'll find many. I recommend games that help young children learn English or Korean.

When they go to elementary school, they might see friends playing games they like and want to play too lol

For a 7-year-old, I think games like Nintendo's Ring Fit Adventure where you can dance along to routines would be good~

For a 7-year-old, I'd recommend games that are cute and have a slower pace. This game requires quick reflexes, so I'd suggest something like a spot-the-difference game.

Wouldn't Nintendo be the best? Players don't make in-game purchases.

I don't really recommend The Battle Cats because some things in it seem a bit weird sometimes. Instead, I recommend Animal Crossing: New Horizons!! There's no need to spend money, it's peaceful, and it's healing.

How's Brawl Stars? You can definitely play and have fun without spending money. Lots of adults play too, and I think kids would feel a sense of accomplishment if they reach 'Brawl Stars' (a high tier). Also, as long as you're not at super high ranks, everyone's just playing for fun, win or lose.

If you're looking for a game to play with your child, I recommend Pokémon GO. You can catch and trade Pokémon together while out and about, which is great for communicating with your child.

Minecraft is pretty much the standard, isn't it?

I think it's good.