You know, you're right. The pectoral fins are set back to far. Seems to me the easiest way to tell the difference is their pectoral fins. The bluegills are set forward more and will reach the tip of the fish where as the greens don't seem to.
Those are definitely green sunfish, Lepomis cyanellus. The mouth is much too big for bluegill, and you can see the chromatophors(little black specks) on the sides that indicate green sunfish. Bluegill don't have these. They don't develope the white/orange/yellow/whatever margins on the fins until they reach a larger size. If that looks like a bluegill, either get your eyes checked, or learn a little more about the fish in your backyard.
