I volunteer with a group called EPIK and we have a bunch of donated laptops which are far too low spec to run the main Minecraft release. But they run Minetest just fine!
Minetest was a big hit, I set the kids the challenge of digging to the bedrock... "That's easy!" they all said, while I sat there cackling evilly.
Anyway, here are some photos! :)
Me setting up all the laptops. It was very short notice and I had to set it all up on the day, managed to get it all up and running on time thankfully. They are all very old atom based machines running Xubuntu, using the minetest PPA. I also somehow ended up looking like a serial killer.

All laptops set up and ready to go

The space filled up pretty quickly

So we installed it on some Android tablets too.

All in all everything went great. We are hoping to integrate minetest into our events now and get the kids learning some LUA while having fun. Thanks folks and keep up the good work! :)