It turns out a lot of what they were doing while "playing video games" was learning how to make really complex and unique game scenarios using minecraft command blocks and redstone -- essentially creating both a RPG PvP arena and a multilevel party dungeon crawl w boss fights.
I run a small minecraft server for them to play and experiment on and I've resisted the urge to try to teach them anything about setting up and running servers, backing up data, or using text editors with syntax highlighting or source control to edit and preserve their command block commands.
I just show up for demos and let them know how cool what they're doing is and backup and reboot the server as needed.
I've messed up plenty as a parent but i think not trying to turn their interest in programming within minecraft into a learning experience has been one of my better decisions.