PC gamer dad trying to get his son into PC gaming with steam

The story behind my question:

My son turned 8 today.

When I was his age, I had already been playing on my Nintendo NES for a while (at least whenever my older brother was willing to let me use it).

A few weeks ago, he asked if he could try some games from my Steam library on my PC. I have quite a few games, and while browsing through them, he got interested in Planet Coaster.

After just a few minutes, I quickly realized I had forgotten a crucial part of his education:

How to use a keyboard and mouse.

As a proud PC Master Race dad, handing him a Switch 2 isn't really the direction I want to go. 😄

So I started thinking about my own childhood. How did I learn to use a computer?

My older brother would just put a CD into the family computer and say, "You'll like this game. Have fun."

No tutorials. No explanations. Just trial and error, experimentation, failures, and eventually figuring things out.

So I decided to do the same thing with my son and bought him Tiny Glade.
https://store.steampowered.com/app/2198150/Tiny_Glade/

At first, he struggled a lot. Holding his dad's oversized gaming mouse in his little hand, right-clicking, click-and-dragging, moving objects around, controlling the camera…

It was actually pretty cool to come back an hour later and see how much progress he'd made. Starting from a few simple shapes, he was already building a nice little landscape.

Now he's getting reasonably comfortable with the mouse and is even starting to combine it with a few keyboard shortcuts.

My actual Steam question:

I'd like him to have his own Windows account and, more importantly, his own Steam account.

I'd also like to be able to control which games he can access.

Considering the size of my Steam library, is there a way to share only some of my games with him? Do I need to create a separate Steam account and buy everything again? What's the best way to handle this?

MERCI !!!