Chrissy,
I have an iPad 4 and can manage it fairly easily. The thing to remember is that the robot will only stretch or shrink if you tap his head, keep holding your finger down, and then swipe; so I suggest trying to place your fingertip more or less solely on his head before you swipe...(I know he's smaller in some screens, so it's not always easy to do.) Hope that helps.
Edit: Actually, this is mentioned on the first screen/location in the game:
But I suppose that might be a tad confusing as you really need to tap *and hold*, not just tap...with tapping and holding being the touch equivalent to clicking and dragging on the old computer.
