Complex sentence: She agreed to allow him to visit Daniel at weekends but, after a few months, Ken found all the travelling and emotional strain of visiting his son too difficult and ceased contact with Denise and Daniel.
Split into simpler sentences: She agreed to allow him to visit Daniel at weekends. But, after a few months, Ken found the long distance travelling and the emotional strain of visits to his son too much to bear, and he ceased contact with both Denise and Daniel.