I think the answer to your question depends on the hunting objective. I have a 4 and 2 year old, and if I wanted to fill a limit of what ever I had better leave the kids at home. If I want to spend the day with my kids I would take them hunting. The 2 are not mutually exclusive, but after the kid gets bored with looking at an empty sky, they immediately become mutually exclusive.
I am learning how to be a good dad, while my kids are learning how to put in some time trying to accomplish a goal.
Keep the trip short and keep the kids comfortable from the elements and you will all have a good time no matter how many ducks you get. I am learning that is all that really matters. Before I had kids I would be there daylight to dark or the limit was filled. That is how I scored a good day. Now I am learning to be content with spending some time with the kids and bringing home a partial bag limit, no limit, or a whole limit.
A month ago I took my 4 year old clam digging at longbeach for razors. When I would start digging, he would dig along side of me,usually tossing sand in my hole, or on the lantern.

Once I made my couple scoops with the shovel and got down on one knee to reach for the clam, he would do the same. Once I got ahold of the clam I would ask where grandpa was, He would look up and point to grandpa, when he would look back down he would find a clam in his hole, right on top. :grin: He would pick it up and want to know where my clam was.

He filled the entire limit of 15 to my 0 and located grandpa 15 times without exception. He talked about how many clams he found until he fell asleep on the way home. He now wants to go back and take mom. I would call that a very very successful trip.
I hope your duck hunting trip turns out great.