Actually, a Minecraft server isn't a bad idea. My youngest (at 8) is obsessed with Minecraft on the Wii U, but the worlds he creates and hosts on that are only available when he runs that game and hosts them (even if he has lots of friends on the platform that connect). I'll have to look into whether the Wii U connects to regular servers or only Wii U specific ones and whether I can host a dedicated one.

I actually have a Pi as well I have't used yet, but was thinking of tinkering around with Redox Os on that.