Thousands attended pre-opening festivities this weekend at Cox Farms — where families enjoyed an outdoor bandstand, cow milking and honey dipping — as the farm staff prepares for the fall festival that starts Saturday.

The tourist attraction, located off of Braddock Road and Pleasant Valley Road, is one of Centreville’s worst-kept secrets and is celebrating its 40th year in Fairfax County. The family opened a small farm in Herndon in 1972 and in 1979 moved to Centreville. Fields of Fear, a haunted field, and the Fall Festival now attracts tens of thousands of people every year (even Malia and Sasha Obama paid a visit last year, the family said).

The farm staff uses the preview weekend to gear up and work out any kinks. There were no major problems reported, although the farm was at near capacity for the weekend, staffers said.

“We get lots of people coming here from all over the place,” said Robby Schmidt, 16, who was working at the farm for the second straight year. “This weekend was a very busy weekend, but it also gets real busy on Columbus Day because people travel to get here.”

Danni Mullin and her daughter Sara came with a group from Fredericksburg. This was the second visit in two years and they said they noticed that the farm had grown quite a bit.

“It’s a real nice place and really a great place to take the kids,” Mullin said.

Louise Keho, of Fair Oaks, brought her two kids, Mitch, 8, and Evie, 5, to try out the water sluice where youngsters can pan for faux gems and minerals.

“I’ve brought them here every year,” Keho said. “They have been here every year since they’ve been babies. We just love this place.”

Bill and Diana Leineweber, of Centreville, brought their grandchildren to the festival, which is something of a family tradition for them.

“We’ve noticed that it gets bigger every year,” Bill Leineweber said. “It’s something that the kids really enjoy.

Co-Farmer-In-Chief Lucas Cox-Galhotra, the son of Eric Cox and Gina Richard (who founded Cox Farms), said the family has been concentrating on growing the farm since they closed the farm’s outlet operation in Vienna two years ago. For this year, they have changed the route of the Halloween hayride and erected a barbecue/pulled pork stand, among other things.