So that's the plot, and in the end, it leaves you with hope that things will get better, but never really pounds that point down and gift-wraps a sappy, happy ending, but it doesn't need to--the plot is just a vehicle to tow all of the gags with.
They belonged in the film--not 'becuase their daddy is the producer'--but because they added big-time in both the many comedy scenes they were in, but also in the movie's scattered drama moments.