Can I reduce or omit the sand if using pea gravel to make a pre-formed exposed aggregate slab?

The Sand helps give it some abrasion resistance. If you want more stone to be exposed then you can seed the surface with added stone when you are finishing the concrete. They do the same to get the Chattahoochee concrete look. The stone is in the mix and is broadcasted on the surface, then troweled in. Then they expose the excess stone on the surface.