Please don't go sit out on a dike and sky bust and wound many birds.
I hunt Ogden bay, Howard and Harold crane a lot for swans.
This year the group I usually hunt with now of Drew out for swans. So if your willing to meet up with me I could take you have your son out on my boat.
We have swan decoys and get birds very close to the boat. Last year we killed 3 in one day. I killed mine with a 20 gauge I shot and it was died before it hit the water, it was only about 10 yards.
So you can pm me and I could help you and your son.