Yea that is kind of what I was leaning too. My current thinking is to find large bodies of water and set up close to them and try to find out where the ducks are going once they take flight and set up there.
Say how old is your son? I took my 9 yr old with me two weeks ago and we had an amazing time.
Chech this out...
http://www.youtube.com/watch?v=i6aXxCYePNk