Throwing a Party

Martin and Sylvia want to throw a party for their parents and their friends, the Webers.  They work it out with Daddy that they can earn the money to pay for decorations and food by doing extra cleaning around the house.  They work all day and then shop for what they need.  On the day of the party, they feel a little nervous - what will it be like?  Will everyone enjoy themselves?  And then the doorbell rings...