In this case I chose Lua not for its suitability to the problem but because the computer my child has is a NetBSD machine with few things besides Lua installed on it.
Not even connected to the internet! Whicih is why I picked a BSD -- fairly complete on its own. We'll see how long I can keep it up. I hope to make "connecting to the internet" a temporary thing done for a specific purpose and then one disconnects.