I'm trying to find some educational PC games for my young niece and nephew. Here's what I have so far.

Scribblenauts (Not on GOG)
Epistory - Typing Chronicles
Minecraft (Not on GOG)

These might not be the best suggestions if your niece and nephew are a bit too young, but maybe some food for thought:

Rocksmith 2014 (not on GOG)
RPG Maker (not on GOG)

Rocksmith requires a real guitar that you can plug in, but if they have an interest in learning to play it could be great fun. RPG Maker (no particular version) I include if they seem to be the kind of kids that would enjoy making a simple game. A little bit complicated, but not too tough (and certainly easier than a full-blown gamedev engine) - or you might even consider games that have easy-to-use level construction kits (though you may have already ticked that box somewhat with Minecraft).

One other thing you might try is searching on Steam in the tag browser for 'Education'. Lots of possibilities, I'm sure - and a number of them will be available on GOG, too.

All the programming games could be considered educational, depending on how much credit you give them for intelligence.

In particular, the Tomorrow Corp games (Human Resource Machine, 7 Billion Humans) are probably targeted towards younger audiences, or at least less experienced ones. The Zachtronics games may need a little more vetting, but it wouldn't hurt to get them advanced games that they can play when they feel more comfortable with them.

I would've also recommended Sokobond, which is indirectly educational, but it's no longer on gog (and I don't recommend non-free games not on gog any more).

darktjm has just made me think of the Incredible Machine games (which ARE available on GOG).

I seem to remember these ones being pretty good, may be a bit tricky to find though:
- Math Ace (There was also an expansion pack for higher grade mathematics)
- Word City (Done by the same people as Math Ace, Math Ace is the better of the two)
- Operation Neptune ( LINK )

There was one other version of Math Ace called "Math Ace JR" but it was for a very young audience and I wouldn't recommend it...

From what I can remember Math Ace itself is very solid if you can find it. ( Here is a link to a Vid Review of it. )

I'll attach pictures of the game boxes I found of Math Ace and Word City just in case anyone is curious.

If you want a real winner though, it is this game: The Typing Of The Dead.

It is an educational conversion of The House of the Dead 2 arcade machine. It looks like the team that did the conversion really put work into it as the game is actually pretty fun.

Here is a video review of The Typing of the Dead, highly recommend this one. ( LINK )

Any titles by MECC or the Learning Company from about 1980 to 1995 should do.

Treasure Mathstorm, Reader Rabbit, etc.

I agree with RedRabbitRun. You can't really go wrong with the Incredible Machine series, excellent logic puzzle games.

They're from the '90s so the graphics are somewhat dated but I've gotta shill for Pajama Sam Vol. 1 and Vol. 2 (though Vol. 1 is the better deal). Beware that the Steam versions have more languages though, and other Humongous Entertainment games are on Steam but not here so I wouldn't blame you for going with the Steam versions. They may be on sale during the summer so you may want to wait for that, since when they do go on sale it's usually -60%.

https://www.youtube.com/results?search_query=pajama+sam

https://www.gog.com/game/pajama_sam_vol_1, https://www.gog.com/game/pajama_sam_vol_2

https://store.steampowered.com/sub/42723/

Thank you for sharing

If they're in middle School or above, Civilization IV had been used in classrooms to teach about internation relations and world history.

Neverwinter nights was made into a game called Colonial, but I can't find it anymore. However, the MIT group has made many games since, here: https://education.mit.edu/project-type/games/

RPG Maker is software, not a game.

Also, early Maxis games are known to be quite educational.

Enjoyed the Carmen Sandiego games growing up. investigative games where you solve crimes using different academic studies depending on the game (History and Geography are primary but there are also Math games).

I would recommend newer versions of Carmen Sandiego though for actual learning as Geography has changed considerably over the years so the older games may not be accurate due to the changes of time.

When it comes to ancient times and history.

Age of Empires (campaigns + encyclopedia)
Age of Mythology (campaign + encyclopedia)
Titan Quest - While the main story is mostly made up, the majority of side quests is based on existing ancient tales. You visit various historical locations, learn names of weapons, shields, armor, materials etc.

Something a bit more mature - Ancestors Legacy (campaigns).

These games are some of the best edutainment I've played so far.

Algodoo is a free 2d construction and physical simulator.