I'll be as honest as possible with you - teach them BASIC, despite what Dijkstra said and despite what the high priests of computing may say about what Dijkstra has said.

The reasons why -

Children need to see the results of their work instantly, and by results I mean that they can ship their code in an executable format that another kid can click on and run without having to load runtimes or libraries. A lot of BASIC dialects are compilers, like FreeBASIC and QB64.

A child who has learnt BASIC can quickly make games with actual sprites without having to look for the right library and the documentation that goes along with those libraries. A lot of people will tell you that Python comes "with batteries included" but you'll find that you always need something else to actually ship an executable that does everything you want - with python you'll need to learn how to use pygame with it and good luck for shipping an executable - with most versions of BASIC the documentation is complete and accessible and to compile code you just press F5 or F9, depending on the compiler or interpreter. With python it's good luck again to make something run really fast - that genetic algorithm you felt crazy enough to write? The high priests will tell you "Oh you'll have to use CPython for that speed boost". Maybe you're just making a cool plasma effect or fire effect, well good luck again in python - in FreeBASIC when you use the PSET function it runs well enough, using pointers it's really fast.

About that compiler or interpreter thing. Some BASIC dialects compile code to machine code, others turn your code into an intermediate language and run that. Most good dialects will allow you to ship executables.

There's a BASIC for every platform out there and the dialects by the different vendors out there are similar enough that you will be able to port code easily. FreeBASIC and QB64 for Linux, Mac, DOS/FreeDOS and Windows - GAMBAS for Linux (which also runs on the Raspbery Pi). BlitzPlus, Blitz3D and BlitzMAX for windows (are now free), RFOBASIC and RCBASIC for Android, Great Cow BASIC for PIC and AVR micro controllers (here's a tutorial for arduino boards https://sourceforge.net/p/gcbasic/discussion/629990/thread/5...)

Modern BASIC is not what Dijkstra was familiar with in the 1960's. Modern BASIC doesn't need line numbers. Modern BASIC does not look like spaghetti code - you can use structured programming concepts and even object orientation to organize your code. And the best part is that you can be done teaching the basics of BASIC in two weeks max and the kids will be able to learn the rest by themselves and ship code immediately after that - whether they want to sell their work or share freely.

As for documentation and tutorials the forums for these dialects of BASIC are very active and you can easily convert code form one dialect to another, so you will always find new and interesting material to teach.

Some useful sites are:

petesqbsite.com

freebasic.net

http://forum.retrogamecoding.org/

http://www.blitzbasic.com/Community/_index_.php

http://games.freebasic.net/

https://sourceforge.net/p/gcbasic/discussion/

http://gambas.8142.n7.nabble.com/

http://www.schoolfreeware.com/QBasic_Tutorials_-_QB64_Tutori...

http://www.bettiesart.com/tc/blitz/

For 3D games programming using Blitz 3D- http://jnoodle.com/Blitz3D/

Demoscene and graphics coding forums
http://www.dbfinteractive.com/

Of course, since BASIC has been popular since the 80's microcomputer boom you can always find lots of old magazines to adapt old programs and games from on Archive.org - MSX BASIC, Acorn/BBC BASIC or Amstrad BASIC magazine code listings should be the most readable.