Set up Duncan with a raspi. give him a custom login / password, butBoot to graphic desktop, skip login terminal.
Net ready, but hide browser? Set up for his home wifi - Ethernet isn’t likely an option.
Raspian OS should be fine.
Scratch - good start to code
Minecraft pi – probably primary use.
Give a pi2, case, power supply, 8gb SD noobs (not bad, maybe $60 – Sean will be cool with that. I’m not going to charge him for my time.)
He has USB wifi dongle, keyboard, mouse and monitor.
Teach about proper shutdown procedures. Don’t just unplug. Maybe give a button-power supply for on / off?