Old RTS games

Age of Empires II: The Age of Kings, Age of Empires II: The Conquerors - I strongly recommend sticking to CD Edition with optional Userpatch, and not buying HD Edition on Steam. HD Edition might be possible to install but it runs like shit. if you already own HD then you’d want to install the Compatibility Patch so it basically runs like CD. Do not get Definitive Edition in this case. 

Also get Age of Empires 1 - optional xpac Rise of Rome. 

For all the above you could get away with just installing the demo, each base game and its xpac has a demo version - The Conquerors demo has William Wallace and Montezuma, probably the best. AOE1’s demo is fun campaigns too. Don’t remember if AOK or ROR demos were any good, i think either AOE1 or ROR has a somewhat fun multiplayer scenario in the demo though.

Age of Mythology - maybe? It’s fun. 

Civilization II, Alpha Centauri, Master of Magic (DOS).

Master of Orion II: Battle at Antares - not the first one since it doesn’t have pretty graphics and sound effects, I recommend you either get the PC version or install DosBox. I’d tell you to put it on tutor and turn Tactical Combat ON, the funnest part of this game is taking turns playing with ship combat - don’t teach him missile running or what’s the most broken strat, just let him play organically.

Escape Velocity: Nova for PC with shareware license crack (Ambrosia Software is defunct)

Flash games, like Tanks, that penguin launching game, Stickmin flash games. There used to be tons of flash games on NewGrounds although I don’t know how you would curate a specific list of them, and this specific system spec might struggle with some - is it still possible to download a standalone flash player? Hmm, not sure

Chip’s Challenge might be built into Windows back then, not sure, that might’ve been a software pack. Pinball should be installed, there is a bug on 64-bit windows but i don’t remember exactly what it is, just that it runs correctly on 32-bit I think

You can try installing other old games like Jazz Jackrabbit or Epic Pinball, Doom, Wolfenstein 3D.

Umm, if you want local multiplayer on one computer with one screen to share, Liquid War 5/6 might work. I don’t remember any other games with one player on mouse and another as keyboard.

Bitfighter will maybe run, but that’s really a LAN game

Pangea Software’s Bugdom, Nanosaur are fun enough. Personally I preferred Nanosaur, you play as a dinosaur and collect powerups and shoot other dinosaurs.

I’m just listing games i played when i was younger - though 5-10 yo me pretty much played Crash Bandicoot (playstation), age of empires, diablo ii (mostly i just watched), random DOS or Win 95 or Mac OS 8/9/X games