The suggested method of play as per the Prima Guide is to have Cassandra attempt to marry Don (who is conveniently on the lot) by first doing some high level romantic socials (most likely to get his aspiration meter platinum) and then use the wedding arch. And that is all they really suggest you do.
With the Goth family, Cassandra is the only one I play the same way every time, but the below is typically how the first day goes.
Cassandra to Don: "You dirty, no good, lying, cheating, scum bag; get off my lot and don't ever come back."
Note from author: I honestly wasn't sure who would win the fight when I planned to show them fighting and my notes say to only show the winner if it was Cassandra so I was really happy about this.
Alexander to Mortimer: "Hey Dad, who was that guy?"
Mortimer to Alexander: "I don't know son, but if Cassandra doesn't like him, he must be a pretty bad person."
Alexander to Mortimer: "Do you wanna go play some chess?"
Mortimer to Alexander: "Lead the way."
Alexander runs off to the chess table.
Cassandra to Darren: "Oh Darren, you were right, Don is a man-whore. He was even WooHooing someone while I was there, in his hot tub..."
Mortimer to Alexander: "All right now, you have school tomorrow so it is time for bed."