Oeh a fun question!
At this point in the story, Lucy would be capable of fighting off 2 or 3 ducks. She has never fought anyone/anything and hates hurting anyone.
Damien could end all ducks, I doubt any duck could survive the magic attacks. But he’d prefer to just leave the fight and let the ducks live.
Jake would burn all the ducks with his fire magic without hesitation. Roasted duck for everyone!
Emily could kill up to 10 ducks while yelling that she’s sorry for doing so.