Those shiners in your photos are likely all common shiners and not emerald shiners.

With your large man made stream/falls I'm not surprised you are getting reproduction out of the common shiners. Common shiners do quite well in northern lakes where they can ascend a feeder stream to spawn. Your set up is like a miniature version of that.

Common shiners max out at about 2/3 the size of GSH, so they will likely be a little better forage for your YP and future WE.

When young, common shiners can be easily confused with emerald shiners. Emerald shiners usually max out around 3" with a giant being 5". Common shiners commonly reach 4"-6" and can push 8+".