Overalls from the pattern?

I'm trying to figure out a good pattern to start with to make something like these http://store.mabokids.com/product/frankie-overall-shorts Although maybe the art museum would be better? Any thoughts on the front bib? Looks like something made of two pieces stitched right side together on 3 sides and turned and then attached to short fronts in the same way a bodice is attached to the front of a dress? Or am I way off? Thanks for any tips!