Longoria's spokeswoman, Liza Anderson, would only tell The Associated Press, in an e-mail, that the wedding will be "a big, happy ceremony with lots of family and friends."
Parker has said the cake will be made in France, but has refused to say much more, telling reporters that organizing a wedding is "a girls' thing."
A French official confirmed Thursday that the couple had chosen Vaux-le-Vicomte, a 17th-century chateau 34 miles southeast of Paris, as the venue for their wedding festivities.
Guests reportedly will include Longoria's "Desperate Housewives" co-stars, teammates from Parker's San Antonio Spurs, Victoria Beckham and other celebrities.
The privately owned chateau near the village of Maincy is shielded from prying eyes by 8 miles of high stone walls.
"It's definitely happening there on Saturday," Lionel Walker, regional head of tourism, told the AP. It is "the best free publicity we could ask for."
A small army of guards is expected to lock down the sprawling, 1,235-acre grounds, and a public road leading to the chateau may be sealed off.
A red slash blocking out Saturday in the datebook of the Saint-Germain-l'Auxerroix church in Paris is the only hint that it may be where Parker, 25, and Longoria, 32, will tie the knot. The church, which is across from the Louvre Museum, once served the French royal family.
Paris Match magazine reported the couple would try to give paparazzi the slip by entering through a back door, and that Longoria would change into her wedding dress in the priest's quarters.
Some reports say Longoria has chosen a classic gown by Los Angeles-based designer Monique Lhuillier, while others say she will wear a Vera Wang design.
Longoria will reportedly wear Chanel couture for the civil ceremony, which is rumored for Friday at Paris' City Hall.
She divorced Tyler Christopher, an actor on the long-running ABC soap opera "General Hospital," in 2004, after two years of marriage.