Personally I wouldn't be concerned about using Round Up or a similar product around the edges of a pond. It breaks down rapidly in contact with organic matter. If you want to play it really safe there are lots of commercial semi-aquatic glyphosates you can order. Shore Clear is one that comes to mind. Herman brothers in the resource guide sells lots of herbicides and other pond products.

For grasses I doubt you'd need to add a surfactant as you do with some surface aquatic plants that have absorption resistant.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.