AoE2. I played the hell out of singleplayer back in the day, and with Remastered they both added new ones and improved the storytelling in old ones. Art of War campaign also is a good introduction to multiplayer combat.
If you like historic stuff; you'll like it. There also exists lot of community campaigns
If I were a parent; I'd only install a DNS filter against malware/ads to any device my kid uses until my kid is capable of understanding how to detect one. While I can teach them how to use the internet; it should be up to my kids to determine what they decide to do with it in the end.
But I do know the risks of having an infiltrated device on my local network; and I'm not having that.