updated 06/02/2012 AT 11:00 AM ET
•originally published 06/02/2012 AT 12:15 PM ET
The expecting bride-to-be and fiancé Will Kopelman celebrated their rehearsal dinner at Montecito’s San Ysidro Ranch, a luxury wine-country hotel, the evening before the couple is expected to exchange vows Saturday.
About 100 guests swilled pre-dinner cocktails at sunset on the lawn overlooking citrus trees and a lily pond. Barrymore and Kopelman’s family and friends then headed into a private room the couple rented out for the night.
A source tells PEOPLE, “Guests mingled and seemed to have the best time. When it was time for dinner, everyone gathered in a private dining room. Several guests gave entertaining and sweet speeches.”
Among those helping the soon-to-be newlyweds celebrate: Cameron Diaz, Jimmy Fallon and his wife Nancy Juvonen.
And no surprise Diaz was in attendance: The longtime pal accompanied Barrymore to her final gown fitting earlier this week at the Chanel boutique in Beverly Hills.
Attendees didn’t leave empty-handed, according to E! Online, Santa Barbara olives, chocolate truffles and bouquets of lavender were among the goodies waiting for them in their hotel rooms that evening. (Most of their guests are reportedly staying at the ranch or the Four Seasons in the area.)