Been thinking about this for the future as well, (my boy isn't quite 2 yet, so few years off)
I've been rewatching LGR's Edutainment episodes for ideas for educational games. Only ones I knew of are Math/Word Rescue and Carmen sandiego. I did play a dos Maths game where you were in a submarine, but cant remember the name, Gameplay it was really just a platformer where you had to answer questions to pass stages but I did enjoy it though.
But think most dos games are self censored with the graphics more carton like then life like, wasn't till the end of the dos era did the graphics really get a bit gory.