9 y/o newphew wants to make an 'app' I assume he means a game, will see them soon. Very hard to gauge what a 9 y/o is capable of, I don't see them much as they live overseas.

I suppose drag and drop in Unity should be ok using purchased assets from the store. I could do any scripting.

What other software is there. I have briefly looked at construct 2, kodu, rpg maker, scratch, lego creator websites and I know about gamemaker.

The lego creator looks the best bet however it is pretty expensive.

Has anyone got any experience here.

MIT Scratch, of course! =)

http://scratch.mit.edu/

And awesome lectures by David J. Malan from Harvard:

https://cs50.harvard.edu/lectures/0

I believe he introduces people to Scratch somewhere in this lecture. His lectures are fun, so maybe appropriate even for 9yo =)

I should have said he wants to publish to iPad which I guess will narrow the field a lot.

I was nine years old when I first asked the question :-) A QBasic book is where my father pointed me, and so began my long journey. This was twenty years ago, mind you. I was fanatical about Legos as a child :D

Perhaps something like the Processing language would be a good start for him. I have used it for rapid prototyping...

I first used RPG maker. Was fun and simple to use, you immediately can create nice looking 2D RPG worlds. Had alot of fun googling matching tilesets to suit a variety of different landscapes and cities. Eventually played around with its scripting capabilities and got some simple but cool story stuff going. Recommended.