03/23/2011 at 07:50 AM EDT
For Reese Witherspoon
, apparently everything's relative – including birthdays.
The Oscar winner, who turned 35 on Tuesday, kept birthday festivities within the family. She attended a casual luncheon with her mom Betty, dad John, brother John, and two nieces at Farm Shop inside of one of her favorite spots, the Brentwood Country Mart.
"She seemed very happy and excited," an onlooker says. "She was in a great mood and seemed happy to be spending time with her family."
Witherspoon, who is engaged to marry agent Jim Toth
, watched as her nieces took a ride on a carousel. Then the whole group stopped by the Poppy Store, where a source tells PEOPLE, Witherspoon "helped her nieces pick out presents … She was very sweet to them."
The birthday girl continued the celebration Tuesday evening with a family dinner at Tavern in Brentwood. Along with Toth, Ava, 11, and Deacon, 7, her parents, brother and sister-in-law and nieces, Witherspoon enjoyed her meal in a private corner of the restaurant.
"Reese seemed ecstatic to spend time with her whole family ... [She] was glowing as she enjoyed her dinner next to Jim. Everyone was in a great mood," says a diner. "Jim and Reese seemed very in love and happy."
All in all, said the diner, "Reese's birthday dinner seemed to be a total success."
Leading into her big day, on Monday, according to an insider, Witherspoon headed to L.A.'s Privé Salon. "Reese left the salon with bouncy hair and she looked great," says the source.