Reese Witherspoon and Jim Toth
03/24/2011 at 06:00 PM EDT
It's been a big week for Reese Witherspoon
The actress, who celebrated her 35th birthday
with her family on Tuesday, is expected to marry agent Jim Toth in a private ceremony in California on Saturday.
Earlier this week, Witherspoon enjoyed a celebratory birthday dinner in Brentwood, Calif., with Toth, daughter Ava, 11, and son Deacon, 7, as well as her parents, brother and sister-in-law and nieces.
Witherspoon and Toth, 40, "seemed very in love and happy" at dinner, according to an observer.
In preparation for her big day, Witherspoon also stopped in at L.A.'s Privé Salon to have her hair cut on Monday, according to an insider.
Four years after her split from Ryan Phillippe
, with whom she shares custody of their two kids, the actress found love again with Toth. The two began dating in January 2010 and he popped the question
less than a year later.