eat duck eggs

So I felt the need to post this here. A little backstory, my 2 sisters are allergic to CHICKEN eggs but not duck eggs. They'd been ordering fresh duck eggs for about 2 years and receiving floaters sometimes and I had told them the trick of if it sinks is good, if sinks but stands underwater...

Is there anything that would make my duck eggs UNSAFE to eat? She has laid 3 so far, the first one was smaller than a ping pong ball, the next two much bigger. Basic feed diet with plenty of snacks like herbs, grapes, blueberries, grass. They forage in the 8x16 run (3 ducks total). We have not...