More design stuff for Alby's game

Inspirational Graphics-

I'm not sure how the graphics of the game will be, but from the description this is what I imagined.

Obviously the first thing I thought of was a 2D side-scroller:

I also like these graphics because they are bold and a little more kidish (that is if we decide in the kid direction).  It would be cool if we could have that detailed of background.

The next thing I thought of is if the game is not 2D then it will be a sort of 3D side-scroller like this:

Ours will definitely not be as detailed, but have the effect that its 3D even though you are in a single left to right point of view.

Questions in general and about core mechanics:

1) Is it going to be 3D or 2.5D?

2) Are we going to have baked-in shadows or generated shadows?

3) Will the ray-casting or whatever its called work?

4) What is the age group?