How do I keep ducks from pooping in my yard?

We have a house on the river and only stay there on weekends in the summer. Our problem is that our neighbor lives there year round and feeds many wild (now tame) ducks. They hear her porch door slam and they come from all over. After they eat they walk to our yard and poop. We have many friends with children that pull up on their boats to visit and play all afternoon. Nobody can walk in the yard or on the beach without out sandals on. Let alone play volley ball or frisbee or have the children nap in the shade on a pallet! We have tried mowing the gr before we start playing but all that does is stir everything (poop) up. We have called the game warden and the local health dept. We have no leg to stand on. One game warden suggested, unofficially, that we trap the ducks and carry them far far away. This lady loves her ducks and my husband and I hate to be mean but we are tired of walking around the tons of little land mines! I welcome your suggestions!!!!