I could see giving kids access to a unix system via guacamole or a similar shell-in-browser solution and letting them run riot.
To help smooth the process of having them program on their own, I send home a writeup with how to install everything on a home computer for different operating systems, how to ask questions on StackOverflow and give an email address I have manned by other students that like responsibility.
I've worked off of them a few times, they're basically useless without internet is the only major drawback - if you connect to a RDP session the battery will last forever.
There are plenty of programming-in-a-browser tools available that are far from painful, plus now that they support Android apps, there's plenty of Android-based programming tools that are non-painful.
We had iPads at one point, but luckily the school realised those were bad and I haven't seen them this year at all.