I had the Island of Doctor Brain as a kid, I enjoyed it and was able to beat it at seven or eight years old but the puzzles might be a bit much for any younger kids (iirc there was a tower of hanoi puzzle that was an interesting challenge) and I’m guessing the first game, Castle of Dr Brain, was at a similar level.

Those were aimed at kids but even those might be too much of a challenge depending on the age of the kids in question. And we’re not even going to talk about how quickly I got stuck in Space Quest as an adult.