Feasibility of using corn seed as a sandbox
So you want to spread a viable, sprouting, organic product several inches deep in a container exposed to the environment?

Hope you like birds, 'cause every flying creature for kilometers will be coming by for lunch.

Also hope you like small rodents, at least the seed-eating types. The local squirrels will love your place.

Also hope you are in a rather arid area. Rain will soak everything and it will start to rot, high humidity will cause things to start growing.

This might be practical if it is indoors. As in climate controlled. An open (or fabric) sided gazebo in the back yard is not "indoors"