EsmsFan

Since both of the engines have a free option, try to use both of them and see which one fits your needs. That should answer your programming pros & cons.

Marketing depends on your skills and not the engine that you use.

Well, since Cocos2d-x and Corona have already been mentioned, you should also have a look at Marmalade.

I am currently trying out Corona SDK and like the fact that it can be used with Lua.

Good looking game. The video of the game on the tablet does not do justice to the quality of the art work.

You could also consider Construct 2.  It's very quick and to get a basic game up and running using built in "behaviours", and programming is done through a visual "event" system.  It's similar to Game Maker, but I think the interface is a bit nicer.

 

Scratch is a good option though. 

Construct2 would be my second choice after Scratch, with GameMaker a close third.

While Gamemaker deserves a nod, I would like to propose Scratch. It has its own site dedicated for educators - http://scratched.media.mit.edu/