Complex sentence: Following the death of her father-in-law, she and her son sell the farm to the Martins (who adopt Timmy and Lassie), and move to the city where she plans to teach music and Jeff plans to attend a science high school.
Split into simpler sentences: Following the death of her father-in-law, she and her son sell the farm to the Martins (who adopt Timmy and Lassie), and move to the city. She plans to teach music and her son plans to attend a science high school.