Mallard duck eggs/nest

My children and I live in a suburban area and have discovered in a flower box in our backyard, a nest of six duck eggs. We are thrilled to witness this sight and potential birth of the ducklings. However, I have been researching with nominal results how we can facilitate the successful birth of the ducklings. I have not seen the mother in a few days, and wonder what are the nesting habits of a female mallard. We have not disturbed the nest, nor let our cat outside for fear he might harm the birds. Please let me know if there is anything else we can do to aid the mallards.