Here are the weaknesses of Huey, Dewey, and Louie I had in mind that FOWL should’ve use those to their advantage from the beginning to weaken the family.
Huey: Being a persnickety and a pacifist despite intelligence.
Dewey: A goofball at times even if he’s full of courage.
Louie: Lazy and greedy with little to no adventuring talents compare to the rest of his family (except for seeing the angles of the situation).