Just for a real-life example, I pulled out Bruce Campbell's biography, appropriately enough titled If Chins Could Kill.  He's got the kind of chin you're aiming for as an adult and the book has pictures of him as a kid.

Basically, the main problem is that you have a mix of child and adult features in your examples.  To get the best one, take your first version and get rid of the chin cleft: keep it big, but make it round instead of flat on the bottom (and certainly not with a cleft).