Mail order brides?

After having our Welsh Harlequin flock in a pen with a designer duck house for about 7 months, I physically carried them to our 2-acre pond, two-by-two under each arm. (They wouldn't go by themselves, always coming into the yard when we let them out instead of going to the pond). I thought they would swim on the pond during the day and come back into the pen at night since the pen is only about 30 or so yards from the pond. But from that day forth, they only came back to their house/pen to eat and would not allow themselves to be caged again (running out whenever they'd see me approach). Predators began picking them off at the rate of one per week, ultimately killing 4 out of 7. We have been down to 3 drakes for about 3 months so I believe they have learned how to survive. My question is, can I buy some female duckings next spring and introduce them to the bachelor ducks to create a flock? Will the drakes accept them if I keep them separate until they're 8-12 weeks old? Will the ducklings follow the drakes so they'll stay out of danger? We won't have eggs like I had once hoped but it seems so sad for the 3 drakes to be alone with no female companionship. Or should I just be happy to have the 3 ducks swimming on the pond and leave well enough alone?