With adult vs. baby eyes, proportionally they're the same width apart. In my life drawing class, we were taught that the eyes are basically and eye-width apart. But because babies have smaller heads, their eyes look farther from one another. Basically, it comes down the ratio of the eyes to head.

As for the cross-eyed problem, I actually think it looks like the opposite, where the eyes are going off in different directions. That's fixable by bumping the pupil of either eye towards the center of the face by a pixel or two. :)