OK hear me out: Minecraft in survival. For real. Nothing jump scares like a creeper going "psshht" in your back, telegraphing that you’re about to die in a destructive explosion. As you walk a narrow path over a chasm of lava in the Nether, the wail of the Ghast might make you fall out of sheer panic before it even shoots at you. The Warden is a special kind of scary too, as it’s nearly unkillable and will detect you by the noise you make. It sounds kind of silly but there’s plenty of players making the remark that Minecraft survival is basically horror.

And it’s all in a child friendly, non gory, voxel style.

Might still be a little too intense if Luigi’s Mansion is your starting point, but Bendy and the Ink Machine is basically a mix of Bioshock and Amnesia but for kids. It has a great 1930s cartoon aesthetic.

Dont Starve is pretty dark... i wouldnt call it horror exactly but it has a spooky vibe. Its officially 12+ but I think a horror-loving kid would probably be fine with it.

It’s on the tip of my tongue; there was a whole series of ghost pirate themed “hidden object” point and click puzzle games. I’ll update the post when it comes back.

Edit: Nightmares of the Deep

Take a look at Dredge! It’s a creepy horror-ish game where you play as a fishing boat. There are some creepy elements at night but it’s fairly causal overall. I really loved the atmosphere and light story elements as well as the fun fishing games that is the majority of the gameplay.

Yes how can we horrify children

Limbo and the other one by the same devs

My kid enjoyed that game where youre a lil kid in a yellow rain coat. Little nightmares

Maybe add the old LucasArts adventure game Grim Fandango to the list, it’s more comical than ‘scary’. It has a relatively recent remaster with modern controls. Some would say the original tank controls are a horror into themselves. Though looking at the ESRB rating it is T for teen.

Lego rock raiders.

Not horror, but can be scary and when monsters arrive it sometimes gave me a jumpscare.

FNaF is a classic, there's no gore or anything like that and a lot of jump scares

A Hat in Time has quite a spooky level in a swamp with a Deal with the Devil involved: https://www.youtube.com/watch?v=vIrPsJMRJmo I also suggest Little Nightmares if the little guy's tougher than he looks: https://www.youtube.com/watch?v=UJ6Jcftf-c4

My Friendly Neighbor hood is mascot horror, but played entirely straight. It's resident evil 4, but with all of the zombies replaced with puppets.

Maybe the 7th Guest. I played that as a kid.

How about Spookie's House of Jumpscares?

At least I think that's what it's called?

I've had success with playing scary games while they watch and when it gets too much I have the characters react in silly ways. Courage the Cowardly Dog, Are you Afraid of the Dark, Goosebumps, etc. You could also try meta horror like Cabin in the Woods, Tucker and Dale. Or something with laugh breaks to defuse the tension like Army of Darkness or Monster Squad.

Has he played the other Luigi's mansion games ?

Luigi's Mansion on the Switch!

are there any good scooby doo games out there? i remember playing one on the PS2 as a kid, good balance of "creepy" stuff like zombies and just goofball humor

Five Nights at Freddy's

If Super Metroid is on the Nintendo Switch emulator, that's a good spooky game, including an explicitly horror-themed level, the Wrecked Ship. There's a layer of removal since it's 2D and zoomed out. Not all of the game is all that spooky, I think it's mainly Wrecked Ship and the end of the game.

Metroid Fusion is much spookier, including sequences where you're being hunted by a Samus clone. Very creepy vibes throughout too. Other M has a lot of thrills as well. And Metroid Dread is, of course, dread-inducing. Actually it was the first Metroid game I couldn't play because the stealth sequences were too much for me, lol.

Majora's Mask is mostly more eerie, but there are some good high tension moments as well.

I would give My Friendly Neighborhood a try - it's very much in the vein of Resident Evil 4 with just-different-enough Sesame Street puppets that give you a jumpscare and damage when they make contact. Put together by John and Evan Szymanski (brothers to and collaborators with David Szymanski, of several New Blood titles fame,) it's made explicitly to be horrifying without relying on gore and excessive violence.

Plants vs zombies maybe?

Hello neighbor might be good. I enjoyed the first one, the rest not so much. But I imagine a young kid would love it.

Maybe the Costume Quest games? They're not scary at all, but Halloween themed.

My 10 and 6-year-old play some horror experiences on Roblox. You'd be surprised how well-made some of them are.

Baldi's Basics

Dead space 2, start him out on the school level for the optimal results.

Also Zombies Ate my Neighbours would be also great for kids, Im not sure what services its available on (but the rom is easy to find for emulation, it is on Snes)

Limbo?

If you're cool with emulation, the PS2 had a game called Gregory Horror Show.

Ghostwire: Tokyo is a good game about ghosts that's not actually that scary. The school DLC for it can get a bit creepy though. Also, Subnautica is one of the scariest non-horror games out there.

Figment?