Lego Racers is an older Lego game and it's a competent kart racer with the added allure of creating your own LEGO cars. Honestly, creating differently themed LEGO cars will remain fun even after you exhaust all the tracks. Lego Racers 2 has a fairly crappy campaign, is less sharp and concise and it has a restrictive building block limit, but it's okay.
Lego Rock Raiders is for a bit older children, but it's basically Dungeon Keeper with LEGO people trying to survive and not peons furthering their master's sphere of influence. Lil' kid will learn the importance of oxygen, too. For the most part, it's fun to crush rocks and uncover new places to build new laboratories and excavators in.
Those old games have enough of a fandom that I suspect there are tweaks to make them run on newer OSes.
Some more oddball suggestions could be World of Xeen with a melee-heavy party. See cute colourful monster - press A 4 times and he's gone. Insane Beggars will give him nightmares is the only downside. Heroes of Might & Magic 1 has fairy-tale like graphics and is the simplest entry in the series, too; I played it at that age. It's all enough of a fairy tale vibe; you'd see more violence in a Heman cartoon. HOMM1 creatures even disappear upon dying instead of leaving corpses.
Aside from that, the obvious answer of Realms of Arkania Remastered.
When he comes of age, play that one Streets of Rage game where at the end you can betray and murder your co-op partner character in a beatdown duel. Then kick him out of the house laughing maniacally.
Oh, and Serious Sam: The First / Second Encounter on hippie mode. Monsters bleed flowers!
EDIT: Remember OGame / Bitefight? I remember when I was at an internet cafe in a southern ski resort and a hobbit next to me got his pimp money in the very aptly named web-browser based game called DZIWKI. No points for guessing what that was and how that website looked like.