Very good idea, I did basically the same thing when i rescued 3 ducks from the river, i used a dog X pen and opened it at the river and began feeding them scratch grains and bread at the back it still took close to a week but these guys had been on the river for a while and were pretty hungry...
Marty I'm thinking to win these this mama duck over quick before preds get her and the ducklings she's gonna have to bring out the big guns[ junk food] just till she gets them home.
Good point, anytime I need to bring my ducks/chickens in from free ranging all I have to do is bring out the bag of W/w bread. works everytime. She'll have to build trust between them before she can bring them home but seems like food is the best way to a ducks heart. Hope you can bring them...