When all things are considered, young adults of today live more satisfying lives than those of their parents, in my opinion.
这句话当中的“when all things are considered”和“in my opinion“都显得多余。完全可以去掉。
改为：Young adults of today live more satisfying lives than their parents.
Due to the fact that our grandparents were under an obligation to help their parents, they did not have the options that young people have at this point in time.
“due to the fact that”就是一个很典型的繁琐的表达方式的例子，可以替换，简化为下面的表达方式：
Because our grandparents were obligated to help their parents, they did not have the options that young people have now.
The farm my grandfather grew up on was large in size.
large 对一个farm来说就是size方面的large，所以in size可以去掉，改为：
The farm my grandfather grew up on was large.
My grandfather grew up on a large farm.
My grandfather has said over and over again that he had to work on his parents' farm.
这里的over and over again就可以改为repeatedly，显得更为简洁：
My grandfather has said repeatedly that he had to work on his parents' farm.