While their kids were at their friends house, Jenny and Jeff parents were meeting. Because the subject of said meeting were said kids and their secret, it happened at Jenny's.
To be honest, most of the meeting was Jeff's father bemoaning how he was missing his ‘missing’ son being at home everyday. "We understand" calmly said Shannon, Jenny's mother "but you have to understand that its what's best for Jenny and Jeff security, that's why Jeff is officially dead. Don't you think your neighbors would be suspicious if they saw Jenny stay the night at the house of her dead boyfriend?"
"You know the existences of monsters need to be a closely guarded secret for the security of said monsters, and that now include our son and his girlfriend" said Jeff's mother to her husband, willingly not saying anything about the fact they only counted as ONE monster.
"But… But… JEEEEEEE–EE–EEFF!!!" Still cried said father.