Possession

I am sending out an invitation to a party. The host couple's last name is "Ferrell". The format is

Dinner

The Ferrell's home

Address

Date

etc.....

Question: Which is correct? "The Ferrell's home" or "The Ferrells' home"

Is the couple viewed as one unit here....thus using "Ferrell's" or as 2 individual people (Ferrells')