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.
The situation that resulted in my grandfather's not being able to study engineering was that his father needed help on the farm.
从意思上来分析，上面这句话需要表达的重要的概念是“grandfather's not being able to study”。
My grandfather couldn't study engineering because his father needed help on the farm.
There were 25 cows on the farm that my grandfather had to milk every day. It was hard work for my grandfather.
My grandfather worked hard. He had to milk 25 cows on the farm every day.
My grandfather worked hard milking 25 cows daily.
Dairy cows were raised on the farm, which was located100 kilometers from the nearest university and was in an area that was remote.
The dairy farm was located in a remote area, 100 kilometers to the nearest university.
In the fall, not only did the cows have to be milked, but also the hay was mowed and stacked by my grandfather's family.
本句不够简洁的原因是本句的重心应该是“忙碌的家庭-my grandfather's family”。
In the fall, my grandfather's family not only milked the cow but also mowed and stacked the hay.