Oooh, tough question. Some on this board say they wash their eggs with no ill effect; others say they won't dare wash an egg, no matter how filthy.
Those Sebastopol eggs are pretty precious, I'd imagine. If it were me, and seeing that there are only four, I'd set them just the way they are-- I wouldn't take the risk of introducing bacteria into the egg by washing it.
Remember, waterfowl nests tend to be a lot dirtier and muddier than chicken nests-- my ducks and geese deliberately bury their eggs in the muddiest, wettest spot they can find, and their eggs still hatch, so. . .