I'm not sure of this, but I got really pissed lookning for giant eggs too, and I started mindlessly attacking the chickens(to no avail of course). But the next time I entered the village i found a giant egg. I did it again and came back to the village to find 2 giant eggs. As I said not sure if this is just a coincidence or not but it might be worth a try.
I tried a number of times to find the giant eggs by reloading the village area from north gate and I also tried setting the time/date forward and then reloading my saves and I still could not find any at any of the treasure spots in the village. I then ATTACKED the chickens as said above ^^^ and found a Giant egg in the same area as the chickens without reloading the area. I think it is possible attacking the chickens triggers it... as strange as that may sound!